The United States Strategic Bombing Survey was established by the Secretary of War on 3 November 1944, pursuant to a directive from the late President Roosevelt. It was established for the purpose of conducting an impartial and expert study of the effects of our aerial attack on Germany, to be used in connection with air attacks on Japan and to establish a basis for evaluating air power as an instrument of military strategy, for planning the future development of the United States armed forces, and for determining future economic policies with respect to the national defense. A summary report and some 200 supporting reports containing the findings of the Survey in Germany have been published. On 15 August 1945, President Truman requested the Survey to conduct a similar study of the effects of all types of air attack in the war against Japan.
The officials of the Survey in Japan, who are all civilians, were:
Franklin D'Olier, Chairman.
Paul H. Nitze,
Henry C. Alexander, Vice Chairmen.
Harry L. Bowman,
J. Kenneth Galbraith,
Frank A. McNamee, Jr.,
Fred Searls, Jr.,
Monroe E. Spaght,
Dr. Louis R. Thompson,
Theodore P. Wright, Directors.
Walter Wilds, Secretary.
The Survey's complement provided for 300 civilians, 350 officers, and 500 enlisted men. Sixty percent of the military segment of the organization for the Japanese study was drawn from the Army, and 40 percent from the Navy. Both the Army and the Navy gave the Survey all possible assistance in the form of men, supplies, transport, and information. The Survey operated from headquarters in Tokyo, with subheadquarters in Nagoya, Osaka, Hiroshima, and Nagasaki, and with mobile teams operating in other parts of Japan, the islands of the Pacific, and the Asiatic mainland.
The Survey secured the principal surviving Japanese records and interrogated top Army and Navy officers, Government officials, industrialists, political leaders, and many hundreds of their subordinates throughout Japan. It was thus possible to reconstruct much of wartime Japanese military planning and execution, engagement by engagement and campaign by campaign, and to secure reasonably accurate data on Japan's economy and war production, plant by plant, and industry by industry. In addition, studies were made of Japan's over-all strategic plans and the background of her entry into the war, the internal discussions and negotiations leading to her acceptance of unconditional surrender, the course of health and morale among the civilian population, the effectiveness of the Japanese civilian defense organization and the effects of the atomic bomb. Separate reports will be issued covering each phase of the study.
In this Summary Report the civilian officials and directors of the Survey have not undertaken to write a history of the Pacific war, nor to apportion credit for victory among the various component Allied forces. They have undertaken, as civilians, to present an analysis of the factual material gathered by the Survey and their general appraisal thereof as to the future.
The attack on Pearl Harbor was designed around surprise, the range of carrier task forces, and the power of aircraft to sink surface vessels. It was executed with the loss of 29 Japanese pilots. Two days later, the Japanese found the British battleship, Prince of Wales, and the battle cruiser, Repulse, without air cover off Malaya and sent them to the bottom with the loss of 4 Japanese Navy medium bombers. Allied air power in the Philippines, Malaya, and the Dutch East Indies was virtually eliminated, mostly on the ground, in a matter of days. Those enormous areas, once local allied air power had been eliminated, were laid open to occupation in a matter of weeks, at a cost of less than 15,000 Japanese soldiers killed, and with the loss from all causes in the entire campaign of 381 Japanese planes.
As these achievements indicate, the Japanese started the war aware of the fact that major offensive action cannot be undertaken without local control of the air. They also appreciated the vulnerability to air attack of surface objectives, both on land and at sea. The Japanese failed, however, to appreciate the full scope and complexity of the requirements for continuing control of the air. The Japanese aircraft production program at the start of the war was inadequate, as the Japanese subsequently discovered, not only in relation to that of the United States, but even in relation to the capabilities of their own economy. Their planning and execution with respect to training, maintenance, logistics, technical development, intelligence and full coordination with their land and surface forces, were limited in relation to the requirements that subsequently developed. Japan's war plans did not contemplate, nor were its capabilities such that it could have contemplated, interference with the sustaining resources of United States air power.
December 7, 1941, found the United States and its Allies provocatively weak in the Pacific, particularly in land and carrier-based air power. The Allied air groups actually in the Pacific were not only few in number but, in large measure, technically inferior to those of the Japanese. The Japanese strength had been underestimated. Ninety P-40s and 35 B-17s in the Philippines could not be expected to check the Japanese push southward. Three of our seven aircraft carriers were in the Atlantic and one training in the Gulf of Mexico. Even at that time, however, we had begun to see, more clearly than the Japanese, the full scope of the basic requirements for air power. Our programs for training, production, maintenance, logistics, and intelligence were limited, not so much by a lack of concept as by the time required for their development and fulfillment.
How the original Japanese advance was stopped, how we achieved air superiority, at first locally, but subsequently more and more generally, and over areas deep within the one-time Japanese dominated areas, culminating finally in air supremacy over the Japanese home islands themselves, and how that air superiority was exploited, is the story of air power in the Pacific war and the subject matter of this Summary Report. The role of air power cannot be considered separately, however, from the roles of ground and naval forces nor from the broad plans and strategy under which the war was conducted.
This decision to which the Japanese were, in effect, committed by mid-October 1941 was based upon the following evaluation:
Certain civilian and naval groups were familiar with the United States, its industrial and technological potential, and probable fighting determination when aroused. They expressed doubts about a strategy which promised no conclusion to the war other than negotiation, and which thus might drag out interminably with consequent risk of defeat. The Navy, however, was gravely concerned about its declining oil supply after the United States and the British economic embargo of July 1941. Such civilians as were reluctant were overruled and went along with the more dynamic opinion.
None of the responsible Japanese leaders believed that within any foreseeable period of time Japan could invade the United States and dictate peace in the White House. Admiral Yamamoto's supposed boast that Japan would do so was in fact never made. These leaders furthermore felt that Japan's limited shipping would be strained to the utmost in providing logistic support for the plan adopted and would be wholly inadequate for any more ambitious program, unless the initial operations went unexpectedly well.
|Army Unit||Aircraft Strength||Deployment|
|Third Flying Division||550||Malayan Campaign|
|Fifth Flying Division||175||Philippines Campaign|
|First Flying Brigade||150||China|
|Second Flying Division||450||Manchuria (Reserve)|
|First Flying Division||50||Japan|
|Naval Unit||Aircraft Strength||Deployment|
|Twenty-first and Twenty-third Air Flotillas||300||Philippines Campaign|
|Twenty-second Air Flotilla||150||Malayan Campaign|
|Twenty-fourth Air Flotilla||50||Marshalls|
|Carrier Force (6 CVs)||400||Pearl Harbor|
|Combined Fleet||75||Seaplanes attached to surface vessels|
The Japanese were not depending solely upon the volume of their air strength in these initial engagements, although they believed they possessed sufficient superiority in numbers over Allied air forces in the Pacific. More than on numbers, the Japanese relied on surprise and speed of advance, and upon the training and experience of their airmen. In 1941 the average first-line Japanese pilot had about 500 - 800 flying hours, and about 50 percent of Japanese Army pilots and 10 percent of Japanese Navy pilots had had actual combat experience in China or in border fighting with the Soviet Union in 1939. The carrier air groups were especially trained in shallow-water torpedo drops for the Pearl Harbor attack, and the Japanese Army air units were trained for support of ground operations in Malaya and the Philippines.
Facing the Japanese, the United States and its Allies had the following land-based air strength in the Pacific:
|U. S. Army and Navy Air Forces||182||Philippines|
|Royal Netherlands East Indies Air Forces||200||Netherlands East Indies|
|Royal Air Force||332||Malaya|
|Royal Australian Air Forces||165||Australia, Solomons, Netherlands East Indies, and Malaya|
The majority of these planes were of obsolete types.
These forces were quickly overwhelmed. Fifty percent of the planes were destroyed on the ground. Our three lightly supported aircraft carriers in the Pacific did not constitute a sufficient force to warrant their being risked in those operations.
Following the initial successes at Pearl Harbor, Malaya and in the Philippines, Wake and Guam were occupied in December, and Rabaul in January. The Japanese gained air superiority in Burma with the loss of 102 planes and, with troops specially trained for jungle fighting, occupied that area at a cost of 7,000 soldiers killed. At the end of 4 months of war, they had carried out the substance of their initial program and with greater ease than they had foreseen. Total merchant shipping losses were 51 ships. Much of the equipment which had originally been scheduled for movement into the southern islands was found to be unnecessary and was left behind in order to achieve greater speed. Certain of the Japanese leaders were concerned by the skillful and unexpectedly determined resistance of our ground forces in the Philippines. They attributed this in part to inefficient Japanese close-air support. But in some circles, the skill and determination with which our isolated forces conducted the defense was correctly assessed as an ominous cloud on the horizon.
Accordingly a new plan was approved, providing for (a) an advance into the Solomons and Port Moresby, to be followed, if successful, by a further advance into New Caledonia, Samoa and the Fiji Islands, (b) the capture of Midway, and (c) the temporary occupation of the Aleutians. Accomplishment of such a program would cut off the line of communication between Australia and the United States, reduce the threat from Alaska,
and deny the United States all major staging areas more advanced than Pearl Harbor.
By stretching and overextending her line of advance, Japan was committed to an expensive and exacting supply problem, she delayed the fortification of the perimeter originally decided upon, jeopardized her economic program for exploiting the resources of the area already captured, and laid herself open to early counter-attack in far advanced and, as yet, weak positions.
As it developed, all that we could do prior to May 1942, apart from the resistance of our isolated forces in the Philippines and sporadic carrier and land-based air raids, was to build up our strength in Australia and the islands lying between Pearl Harbor and Australia, while bringing to fruition our training and production programs.
Similar intelligence provided advance information as to the Japanese move toward Midway in June. In this case, the transports were supported by an advance striking force, including the most powerful surface forces yet assembled in the war and four of Japan's remaining eight operational carriers. An additional Japanese carrier was in a supporting force farther to the north. Again only weaker forces were available to the United States three carriers, the Enterprise, Yorktown, and Hornet, the only ones available for combat action in the Pacific at that time, were rushed to the attack. Our planes located the Japanese fleet and sank three of the enemy carriers, and so damaged the fourth that she subsequently fell an easy prey to a United States submarine. Deprived of its carriers the Japanese Fleet was forced to retire despite its preponderance in heavy ship strength. Survey interrogations of surviving officers from the Japanese carriers indicate that they were sunk by carrier-based dive bombers. Two-thirds of the pilots on the Japanese carriers sunk were rescued by Japanese destroyers. Some of the Japanese carrier-based planes discovered our carriers and succeeded in damaging the Yorktown so seriously that she went dead in the water and was sunk by a Japanese submarine. Except for the finishing off of stragglers by submarines, the combat in this engagement was entirely air action.
Immediately after Midway, the Japanese had 4 carriers fit for action, shortly to be joined by a fifth; but of these only 1 was large. In addition, they had 6 carriers under repair or construction. The United States had 3 large carriers operational in the Pacific and 13 carriers, and 15 escort carriers, either being readied for operation, or under construction. The Japanese Navy, thereafter, was hobbled by its weakness in the air, and could engage our forces only at night or under cover of land-based air until that air strength was rebuilt. A balance of naval air power in the Pacific, and as a consequence a balance of naval power as a whole, was thus achieved at Midway.
The scene of intense conflict shifted back to the islands south of Rabaul, the seas surrounding them, and the air over both. The Japanese had determined to renew their efforts to capture Port Moresby, if necessary by the overland route from the northern shore of New Guinea, and were constructing air fields in the Solomons. The United States Joint Chiefs of Staff ordered a two-pronged attack; one directed toward northern New Guinea from Port Moresby, the other up the chain of the Solomon Islands beginning with Guadalcanal; both with the final objective of capturing Rabaul. General MacArthur and Admiral Ghormley considered the forces available to them inadequate, but, in view of the importance of maintaining the line of communication with Australia, they were ordered to go ahead with what they had. A test of the Japanese perimeter thereby developed earlier than the Japanese had expected.
While the Southwest Pacific command was building air fields in northern Australia, Port Moresby and Milne Bay, the Japanese landed, on 21 July 1942, at Buna on the north coast of New Guinea opposite Port Moresby and infiltrated over the Owen Stanley Range. Their lines of communications were cut by air attacks, their advance columns strafed and their attack held and pushed back by ground forces, in part supplied by air. The Japanese testify that they were unable to reinforce this attack to the extent they had planned because of developments at Guadalcanal.
On 7 August 1942, a surprise landing was made on Guadalcanal. Three United States carriers gave initial air support and the Marines who landed quickly captured the air field (later named Henderson Field) which was under construction by the Japanese. Interrogation of the senior Japanese commanders involved in the Solomons campaign indicates that they originally misjudged the strength of our attack and sent in only one reinforcement battalion of 500 men on fast destroyers from Truk. After this battalion was virtually destroyed, they sent in 5 more which again were not quite sufficient. Finally, they attempted to send in whole divisions. Thirty thousand troops were landed but, by that time, it was too late. Local control of the air provided by planes based on Henderson Field made it possible, but barely possible, to defend our unloading supply ships in the daytime, and made it impossible for the Japanese to land, except at night and then under hazardous and unsatisfactory conditions. The efforts of the Japanese to run in reinforcements at night, and at times to shell our shore installations, resulted in a series of night naval surface engagements which caused heavy losses to both sides. Our air strength was initially limited, was maintained by desperate and irregular reenforcement, and at one time was reduced by enemy naval bombardment to only 5 operational airplanes. The Japanese constructed a chain of air fields between Guadalcanal and Rabaul, and attempted to raid our ships and installations. In the air actions, however, they suffered increasingly heavy losses, not merely in numbers, but also in proportion to United States losses. The Japanese paint a vivid picture of the intolerable position in which inability to achieve air control placed them. General Miyazaki testified that only 20 percent of the supplies dispatched from Rabaul to Guadalcanal ever reached there. As a result the 30,000 troops they eventually landed on Guadalcanal lacked heavy equipment, adequate ammunition and even enough food, and were subjected to continuous harassment from the air. approximately 10,000 were killed, 10,000 starved to death, and the remaining 10,000 were evacuated in February 1943, in a greatly weakened condition.
By the end of 1942, the most serious of the Japanese attempts to drive us off Guadalcanal had been thrown back and Allied operations to capture the Buna area were drawing to a close. We were securely established in these critical areas and had gradually built up local superiority in all arms, air, ground and sea. Our losses had been heavy. The Japanese, however, had suffered a crucial strategic defeat. Their advance had been stopped, their strategic plan fatally upset, many of their best pilots lost, and Allied forces firmly installed in
positions in the Solomons and New Guinea, which threatened the anchor of their perimeter at Rabaul. In opposing this threat, the Japanese committed in piecemeal fashion and lost all of their fully trained Navy air units, including those rescued at Midway, and a portion of their best Army air units. The Japanese never fully recovered from this disaster, the effects of which influenced all subsequent campaigns. For the first time, the few Japanese who had all the facts at their disposal appreciated the seriousness of the situation. Greatly expanded programs for the training of pilots and the production of aircraft, radar and communications equipment, antiaircraft guns and ammunition, cargo vessels and tankers, were drawn up, but time was required to implement them.
The initiative had passed to the United States.
Due to the geography of the Empire, the Japanese ground forces depended for their effectiveness upon overseas support in all areas except the main home islands, and even there, overseas imports of raw materials were required. In China, Korea, and Manchuria, an overwater lift to the mainland was involved, and shipping was employed in the supply of troops in Malaya, Burma, and continental regions of the southwest. The islands of the eastern perimeter were completely dependent on supply by sea. Deployed as the Japanese ground forces were on detached land masses, dependent on inadequate shipping, their defeat was necessary only at points of United States choosing. The bulk of them could be bypassed.
The Japanese Navy, which included two 64,000 ton battleships of great fire-power and speed, had lost both operational freedom and striking power due to its limited carrier-based air strength. By late 1943, the United States had available sufficient carriers for clear-cut superiority in the air, and had added to the fleet sufficient modern heavy ships to offer reasonable protection against the Japanese surface strength were it to be committed under bad weather or other conditions limiting the degree to which our superiority in the air could be brought to bear. The ability to destroy the Japanese surface forces, if they were committed, was essential. Furthermore, their destruction would increase the freedom and ease of our further advances.
The limitations imposed by geography and the range of Japanese land-base planes made it impossible for the Japanese to achieve sufficient mobility of their land-based air forces to concentrate their full air strength against us at any crucial point, prior to the invasion of the Philippines and Okinawa. Most of the island atolls were too small to support the necessary air fields, and in New Guinea, the Solomons and the Marianas, logistic, air field construction and ferrying problems made such concentration impossible. Even within the limits so imposed, poor Japanese staff work and tactics resulted in piecemeal employment of their available air strength. Over and above these weaknesses, Japanese aircraft production, pilot training and maintenance were so far behind our own that it was evident that general air superiority over the Japanese could be achieved. This objective received first priority.
The Japanese shipping target was immediately available. In the first year of the war, submarines, capable of long-range offensive action inside the Japanese perimeter, sank more than 10 percent and air planes 4 percent of the merchant ship tonnage which Japan possessed at the start of the war. The strangulation of Japanese overwater movement, thus begun, could be continued both by the submarine and by attack from the air.
Japanese industry and her home population would not be within effective striking distance of United States long-range bombers until bases within 1,500 nautical miles of Japan could be secured.
An advance to strategic positions across the Pacific would give us bases from which to complete the interdiction of Japan's overwater shipping, to mount large scale air attacks against the Japanese home islands, and to prepare for an invasion of the home islands themselves.
Thereafter, the amphibious advance toward Japan continued over two routes. One was up the north coast of New Guinea to the Philippines, the other across the Central Pacific through the Marshalls to the Marianas and Palau and then subsequently on to Iwo Jima and Okinawa. Basically, the advance was for the purpose of projecting United States power to points which cut Japan's supply lines to the south and were within striking range of the Japanese home islands. Objectives were seized for one or more of four purposes: To provide forward air fields so that shore-based aircraft might maintain and project forward United States control of the air; to furnish advance bases for the fleet; to secure land areas for the staging of troops in succeeding advances; and, in the case of the Marianas, to provide bases for long-range air attacks on the Japanese home islands.
In the New Guinea area it continued to be possible to choose objectives for our advance where the enemy was weak, to seal off these objectives from enemy reinforcement and cover advances to them with land-based air, and, in certain instances, to supply the operation entirely by air. Marilinan, Nadzab and other inland bases on New Guinea, which eventually had complements as large as 25,000 men, were occupied, supplied and later moved forward entirely by air. The range of these advances was limited to the combat radius of fighter aircraft.
For long-range amphibious advances against strongly defended positions a typical pattern developed. Japanese bases flanking the United States objective were smothered by a concentration of air power. Such bases as were within reach were hammered by shore-based air. Carrier-based air and available shore-based air softened the area to be occupied, and as the amphibious force moved up, fast carriers advancing beyond the objective struck swift blows at all positions which could threaten the objective area. With close air support from both escort and fast carriers and a concentration of gunfire from combatant ships of the support force, an amphibious assault over the beaches was made. The objective was secured under air support and cover from the carriers, which were not withdrawn until air fields ashore could be prepared and activated.
The amphibious steps along the two principal lines of advance toward Japan were well timed and mutually supporting, even though concentration on one line might have been more rapid. The losses inflicted at Rabaul, primarily by land-based planes from the Solomons and New Guinea, forced the Japanese to the decision not to support their garrisons in the Gilberts, were they to be attacked. The Central Pacific advance into the Gilbert and Marshall Islands in late 1943 and early 1944, and the threat of a fast carrier task force strike against Truk, which eventuated in February 1944, cleared the Japanese Fleet from the New Guinea flank and assisted the move into the Admiralties in March 1944 and the long step up the coast of New Guinea to Hollandia in April 1944, which was followed by a further advance to Wakde and Biak in May 1944. When the Japanese attempted reinforcement of northern New Guinea, the Central Pacific advance into the Marianas in June 1944, forced the abandonment of the operation. The Japanese committed their carriers in the defense of the Marianas, and lost in the Battle of the Philippines Sea practically all their carrier-based air groups sufficiently trained for combat, as well as three carriers sunk. Noemfoor was taken while the Japanese were preoccupied in the Marianas. Landings on Morotai were timed with those in the Palaus.
While the landings in the Palaus were in progress, the fast carrier task force struck Japanese aircraft, air fields and shipping in the Philippines. Preliminary to the Leyte operation, the fast carrier task force with a concentration of more than 1,000 planes attacked Okinawa, Formosa and the Philippines, exacting a large toll of Japanese air power. B-29 strikes from China against air installations
on Formosa supported this operation. The landing at Leyte Gulf in the Philippines was correctly assessed by the Japanese as their last opportunity, short of a defense of the Japanese home islands, to throw in all their available forces to check the United States advance in a decisive engagement.
Three days after the landing at Leyte they committed their entire fleet in a three-pronged attack. The plan contemplated that a carrier force advancing from the north would draw off our main strength, while heavy surface forces approaching through Surigao and San Bernardino Straits and covered by Japanese Army and Navy planes from airfields in the Philippines would destroy our transports and supporting strength off the landing beach. The Japanese strategy succeeded in drawing off our main strength to the north. The southern Japanese force was destroyed in a night surface engagement in Surigao Straits. Four carriers in the northern force were sunk off Luzon. Although one of its super-battleships had been sunk by torpedo plane attack, the central force penetrated close to our transports still possessed of overwhelming surface strength. The Japanese commander of the central force testified to the Survey that lack of expected land-based air support and air reconnaissance, fear of further losses from air attack, and worry as to his fuel reserves induced him to withdraw. As a result of this decision to retire, the Japanese failed to secure the objective for which catastrophic losses had been risked and suffered by the other two Japanese forces.
In the ensuing actions in the Philippines, the Japanese lost all the troops and supplies deployed there, plus three and one-half divisions sent in from China and Manchuria. In the Philippines campaign as a whole they committed and lost 9,000 planes. On 1 March 1945, the Japanese decided to send no further supplies to their ground forces outside of the home islands. Except for delaying actions they had been forced to concentrate solely on defense against invasion.
While the liberation of the Philippines was being completed, the Central Pacific forces made the difficult moves into Iwo Jima and Okinawa.
Full superiority over Japanese air forces was gradually attained. British ground forces at Imphal which had been surrounded by an attacking Japanese force were supplied by Allied air. The Japanese force was in turn isolated by air attack and destroyed. The troops that liberated Burma were moved, supplied, and supported by air. Japanese logistics in Burma and China were disrupted. China was kept in the war.
Over 1,180,000 tons of supplies and equipment and 1,380,000 troops were transported by air. The air movement over the "hump" between India and China attained a peak rate of 71,000 tons in 1 month.
In the fall of 1943 it was decided to attack Japanese industrial targets in Manchuria and Kyushu with B-29s flying from advanced bases in China. When this decision was reached, Guam, Saipan and Tinian had not yet been captured, and no other bases were available sufficiently close for direct strikes at the Japanese "Inner Zone" industries. The principal bottleneck in air operation in China was the transportation from India by air of the necessary supplies, most of which were allocated to supplying Chinese ground forces. As a result, the B-29s had sufficient supplies for only a small number of strikes per month. Data secured by the Survey in Japan established that these strikes caused more severe damage to the Manchurian steel plants selected as targets than assessment of aerial photography had revealed. With the benefit of hindsight, however, it appears that the overall results achieved did not warrant the diversion of effort entailed and that the aviation gasoline and supplies used by the B-29s might have been more profitably allocated to an expansion of the
tactical and antishipping operations of the Fourteenth Air Force in China. The necessary training and combat experience with B-29s provided by this operation might have been secured through attacks on "Outer Zone" targets, from bases more easily supplied. In November 1944, long-range bomber attacks from Guam, Saipan and Tinian were initiated. The B-29s based in China were transferred to these bases in April 1945.
By March 1945, prior to heavy direct air attack on the Japanese home islands, the Japanese air forces had been reduced to Kamikaze forces, her fleet had been sunk or immobilized, her merchant marine decimated, large portions of her ground forces isolated, and the strangulation of her economy well begun. What happened to each of these segments of Japan's vanishing war potential is analyzed in the following sections.
Japanese army and navy plane losses from all causes, both combat and noncombat, rose from an average rate of some 500 planes per month in the early months of the war to over 2,000 per month in the latter months of 1944. Aggregate losses during the course of the war were of the order of magnitude of 50,000 planes, of which something less than 40 percent were combat losses, and something over 60 percent were training, ferrying, and other noncombat losses.
The Japanese were thus able to increase the numerical strength of their air forces in planes, in almost every month of the war. Numerical strength increased from 2,625 tactical planes at the outbreak of the war to 5,000 tactical planes, plus 5,400 Kamikaze planes, at the time of surrender.
Aggregate flying personnel increased from approximately 12,000 at the outbreak of the war to over 35,000 at the time of surrender.
United States aircraft production and pilot training exceeded the Japanese totals by wide margins, but only a portion of this strength could be deployed to the Pacific. United States first line strength in the Pacific west of Pearl Harbor increased from some 200 planes in 1941 to 11,000 planes in August 1945. It was not until late 1943 that we attained numerical superiority over the Japanese air forces in the field. Even in 1942, however, the relatively few United States air units in the Pacific were able to inflict greater losses than they sustained on the numerically superior Japanese. Aggregate United States plane losses during the course of the Pacific war, not including training losses in the United States, were approximately 27,000 planes. Of these losses 8,700 were on combat missions; the remainder were training, ferrying and other noncombat losses. Of the combat losses over 60 percent were to antiaircraft fire.
As previously stated, Japanese pilots at the outbreak of the war were well trained. The average Army pilot had some 500 hours before entering combat and Navy pilots 650 hours. These experienced pilots were largely expended during the bitter campaigns of the opening year and a half of the war. The Japanese paid far less attention than we did to the protection, husbanding and replacement of their trained pilots, and were seriously hampered in their training program by a growing shortage of aviation gasoline. Average flying experience fell off throughout the war, and was just over 100 hours, as contrasted to 600 hours for United States pilots, at the time of surrender. Inadequately trained pilots were no match for the skilled pilots developed by the United States.
At the time of the initial Japanese attack, Japanese fighter planes, although less sturdily built, more vulnerable and weaker in fire power than the United States fighters, had certain flight characteristics superior to those of United States fighters then available in the Pacific. The Japanese improved the quality of their planes during the war, greatly increased the power of their aircraft engines, ultimately exceeded United States fighters in fire power and had first-class aircraft in the design and experimental stage at the end of the war. They lacked, however, the widespread technical and industrial skill to match the United States in quantity production of reliable planes with increased range, performance and durability. After the initial campaigns, the United States always enjoyed superiority in the over-all performance of its planes. By American standards, the Japanese never
fully appreciated the importance of adequate maintenance, logistic support, communications and control, and air fields and bases adequately prepared to handle large numbers of planes. As a result, they were unable to concentrate any large percentage of their air strength at any one time or place. Neither did they appear to have the ability to control large formations in the air with any degree of efficiency.
Local air control and its tactical exploitation the Japanese understood and achieved in their early offensives.
But along with all other military powers prior to the war, the Japanese had failed fully to appreciate the strategic revolution brought about by the increased capabilities of air power. The ability to achieve general and continuing control of the air was not envisaged as a requirement in their basic war strategy, as was the planned destruction of the United States Fleet. Had this basic requirement been well understood it is difficult to conceive that they would have undertaken a war of limited objectives in the first place. Once started on a strategic plan which did not provide the means to assure continuing air control, there was no way in which they could revise their strategy to reverse the growing predominance in the air of a basically stronger opponent who came to understand this requirement and whose war was being fought accordingly.
From October, 1944, to the end of the Okinawa campaign, the Japanese flew 2,550 Kamikaze missions, of which 475, or 18.6 percent were effective in securing hits or damaging near misses. Warships of all types were damaged, including 12 aircraft carriers, 15 battleships, and 16 light and escort carriers. However, no ship larger than an escort carrier was sunk. Approximately 45 vessels were sunk, the bulk of which were destroyers. The Japanese were misled by their own inflated claims of heavy ships sunk, and ignored the advice of their technicians that a heavier explosive head was required to sink large ships. To the United States the losses actually sustained were serious, and caused great concern. Two thousand B-29 sorties were diverted from direct attacks on Japanese cities and industries to striking Kamikaze air fields in Kyushu. Had the Japanese been able to sustain an attack of greater power and concentration they might have been able to cause us to withdraw or to revise our strategic plans.
At the time of surrender, the Japanese had more than 9,000 planes in the home islands available for Kamikaze attack, and more than 5,000 had already been specially fitted for suicide attack to resist our planned invasion.
vessels after it had been mortally damaged by carrier airplanes.
The Japanese had two Yamato-class battleships, each of 64,000 tons, armed with 18-inch guns and minutely compartmented, which were more powerful than any United States battleship. One was sunk in the Sibuyan Sea, the other south of Kyushu, both by carrier torpedo-planes.
Japan began the war with 381 warships aggregating approximately 1,271,000 tons. An additional 816 combat ships totaling 1,048,000 tons were constructed during the war. Five hundred and forty-nine ships of all types and sizes, totaling 1,744,000 tons were sunk. Approximately 1,300,000 tons of Japanese warships in the carrier, battleship, cruiser and destroyer categories were included in the aggregate tonnage sunk. Of this total roughly 625,000 tons were sunk by Navy and Marine aircraft, 375,000 tons by submarines, 183,000 tons by surface vessels, 55,000 tons by Army aircraft, and 65,000 tons by various agents. Only 196,000 tons in these categories remained afloat at the end of the war. The tonnage sunk by surface ships was principally in night actions. A shortage of Japanese destroyers after 1943 and inadequate Japanese air antisubmarine measures contributed to the successes of United States submarines against the Japanese fleet.
After the liberation of the Philippines and the capture of Okinawa, oil imports into Japan were completely cut off; fuel oil stocks had been exhausted, and the few remaining Japanese warships, being without fuel, were decommissioned or were covered with camouflage and used only as antiaircraft platforms. Except for its shore-based Kamikaze airforce and surface and undersea craft adapted for anti-invasion suicide attack, the Japanese Navy had ceased to exist.
Japan entered the war with some 6,000,000 tons of merchant shipping of over 500 tons gross weight. During the war an additional 4,100,000 tons were constructed, captured or requisitioned. Sufficient information was secured by the Survey in Japan concerning this 10,100,000 tons to tabulate ship by ship, (a) the name end tonnage, (b>) the date, location; and agent of sinking or damage, and (c) the present condition and location of such ships as survived. The sources from which evidence was obtained were in some respects conflicting. Where possible these conflicts have been resolved. The Joint Army and Navy Assessment Committee has tentatively arrived at similar results and is continuing its efforts further to refine the evidence. The Survey believes that the figures included in the following breakdown will not differ significantly from the final evaluation of the Joint Army and Navy Assessment Committee.
Eight million nine hundred thousand tons of this shipping were sunk or so seriously damaged as to be out of action at the end of the war. Fifty-four and seven-tenths percent of this total was attributable to submarines, 16.3 percent to carrier based planes, 10.2 percent to Army land-based planes and 4.3 percent to Navy and Marine land-based planes, 9.3 percent to mines (largely dropped by B-29s), less than 1 percent to surface gunfire, and the balance of 4 percent to marine accidents.
Due to their ability to penetrate deeply into enemy-controlled waters, submarines accounted for approximately 60 percent of sinkings up until the final months of the war. During 1941, carrier task forces made deep sweeps which accounted for large numbers of ships. After April, 1945, when Japanese shipping was restricted to the Korean and Manchurian runs and to shallow inland waters, mines dropped by B-29s in Japanese harbors and inland waterways accounted for 50 percent of all ships sunk or damaged. In isolating areas of combat from ship-borne reinforcements land-based aircraft also sank large numbers of barges and vessels smaller than 500 tons gross weight, not included in the tabulation prepared by the Survey.
In the Survey's opinion those air units which had anti-shipping attacks as their prime mission and employed the required specialized techniques, equipment and training achieved against ships the best results for the effort expended.
The Japanese originally allocated two-thirds of their shipping fleet to the logistic support of their military forces in the field. They expected that
after their original advance had been completed they would be able to return increasing numbers of ships to the movement of raw materials for their basic economy. After the beginning of the Guadalcanal campaign, however, they were kept under such constant and unexpected military pressure that the contemplated returns after that date were never possible.
Up to the end of 1942, ship sinkings exceeded new acquisitions by a small margin. Thereafter, the aggregate tonnage sunk increased far more rapidly than could be matched by the expansion of the Japanese shipbuilding program. The size of the usable fleet thus declined continuously and at the end of the war amounted to little more than 10 percent of its original tonnage. The Japanese belatedly attempted to build up a convoy system, to re-route freight movements to rail lines, and to abandon more distant sources of supply, but these measures acted only as palliatives and not as cures. Furthermore, convoying and re-routing decreased the freight moved per ship by a factor amounting to 43 percent in the closing months of the war. In 1944 tanker losses became particularly heavy and were thereafter the first concern of the Japanese shipping authorities.
The basic economic consequences of ship sinking will be discussed in a later section. From the standpoint of the Japanese armed forces in the field it will be noted that 17 percent of army supplies shipped from Japan were sunk in 1943, 30 percent in 1944, and 50 percent in 1945. A shortage of fleet tankers was a continuing limitation on the mobility of the Japanese fleet and contributed to its defeat in the two crucial battles of the Philippine Sea. Inadequate logistic support, due in large part to lack of shipping, was one of the principal handicaps of the Japanese air forces.
Attacks by submarines, long-range search and attack planes, mines, and carrier and land-based planes were mutually supporting and complicated the Japanese defenses. Long-range air search found targets for the submarines; convoying which offered some protection against submarines increased the vulnerability to air attack; ships driven into congested harbors in fear of submarines were easy prey for carrier strikes; and mines helped to drive ships out of shallow water into waters where submarines could operate. Had we constructed more submarines, earlier concentrated on tankers and more fully coordinated long-range air search and attack missions with submarine operations, the ship sinking program might have been even more effective.
The strategy of our advance and the limitations imposed on Japanese overwater transportation became such that the Japanese could concentrate only a small portion of their available Army ground forces strength at any of the critical island positions which we determined to capture. Japanese soldiers were unique in their willingness to face death and endure hardships. At every point where our Army or Marine forces engaged the Japanese on the ground after 1942, we enjoyed full air superiority. In every instance, except Ormoc in the Leyte campaign, we had eliminated Japanese ability to reinforce the critical area with either men or supplies. At Ormoc the Japanese were able to land 30,000 troops, but these reinforcements arrived piecemeal over too long a period of time to be effective and many of the transports were sunk prior to unloading heavy equipment. In every instance where the Japanese had prepared defenses in a landing area these had been softened up by aerial bombardment and usually by naval shelling as well. It often proved impossible, however, to destroy more than a small percentage of the defending Japanese soldiers in preliminary softening up operations of even the greatest intensity. The Japanese were dug in, in tunnels, trenches and caves which were hard to find and often impossible to destroy, either by bombing or by naval shelling. Most of their fixed artillery positions were eliminated, but even some of these survived. The
weight of fire on the immediate invasion beaches was generally such that the Japanese retired a short distance inland, but once we advanced beyond the beaches, it became necessary to destroy the remaining Japanese in costly close-range fighting. It was demonstrated, however, that Japanese resistance was effectively weakened and our casualties lighter when the appropriate weapons were employed with sufficient weight and accuracy in both preliminary softening up operations and subsequent close support.
A Japanese estimate indicates that in the southern regions, approximately 25 percent of their combat deaths resulted from aerial bombardment, 58 percent from small arms fire, 15 percent from artillery, and the remaining 2 percent from other causes.
In those places where it was essential to eliminate Japanese ground resistance in close-range fighting, great precision had to be developed in air-support operations in order to be certain not to hit our own troops, and to assure hits on the small targets which the critical Japanese positions presented. This required highly specialized training and the closest coordination between the ground and air forces through an intricate system of ground and air observers and unified control by ground-ship-air radio communication. In the Pacific war this system was continuously improved by the Navy and Marines in connection with succeeding amphibious operations against strongly defended positions and reached a high degree of effectiveness. In the Philippines campaign, the Army air forces employed comparable techniques, and General Yamashita has testified to his feeling of complete helplessness when confronted with this type of opposition.
In the Southwest Pacific, it often proved possible to effect landings at lightly held positions, and thus bypass large bodies of enemy ground forces. In the Central Pacific, many of the islands the Japanese expected us to attack were bypassed, and the garrisons left to wither and die. Survey examination of the bypassed islands in the Pacific and interrogation of the Japanese survivors confirmed their intolerable situation. Their planes and ground installations were destroyed by air attack. Cut off from any supplies or reinforcements, except occasionally by submarine, their food ran out. On certain of the islands, Japanese actually ate Japanese. It appears, however, that our air attacks on these bypassed positions were often continued longer and in greater weight than was reasonably required or profitable.
This industrial expansion was based and depended on the availability of raw materials. Great efforts were devoted to the increase of raw material output in the home islands. In some respects, major results were achieved. Coal production in Japan rose from 28,000,000 tons in 1931 to 55,600,000 tons in 1941. Domestic iron mining made considerable progress. Nevertheless, no country could have been farther from self-sufficiency, with respect to raw materials, than Japan. The development of basic material sources on the continent of Asia constituted almost the central issue of Japan's economic policy during this period.
Although progress in Manchuria and China helped significantly to alleviate Japan's raw material shortages in coking coal, iron ore, salt and foods, insufficiency of raw materials continued to be the most important limiting factor on Japanese industrial output. Negligible quantities of oil and no bauxite sources existed within Japan's "Inner Zone." Output of aluminum ingots had risen from 19 tons in 1933 to 71,740 in 1941, 90 percent of which was produced from bauxite imported from the Dutch East Indies. Plans to develop a synthetic oil industry failed to yield significant results and Japan was almost wholly dependent on oil imports from the United States or the Dutch East Indies. A similar dependence on imports existed for rubber, ferro-alloys such as manganese,
chrome, nickel, cobalt and tungsten, and for non-ferrous metals such as tin, lead, and mercury.
Pending seizure and economic exploitation of the oil and bauxite resources of the southern area, stock piling of these vital materials was a necessity. By the end of 1941, bauxite stocks of 250,000 tons, constituting a 7 months' supply, and 43,000,000 barrels of oil and oil products were stored in Japan.
Considering the economic performance of the decade, one cannot but be impressed by the intensity of the effort and the magnitude of the results. Nonetheless, Japan remained with an economy having approximately 10 percent of the potential of the United States economy. It was desperately vulnerable to attack on its shipping. Having a comparatively small, newly developed industry, it had to work without much cushion of under-utilized physical plant capacity. Having had little experience with mass production, the country had no opportunity to build up a large force of industrially and mechanically trained personnel. This meant shortages of skills, ingenuity and ability to improvise later on, when the economy was under the stresses and strains of large-scale warfare.
This economic potential could support a short war or a war of limited liabilities. The accumulated stocks of munitions, oil, planes and ships could be thrown into action and produce a devastating effect on unmobilized enemies. When this initial blow failed to result in peace, Japan, without significant help from Germany, was doomed. Its economy could not support a protracted campaign against an enemy even half as strong as the United States.
In addition, the success of the initial Japanese military operations delayed total economic mobilization until after the defeats of late 1942. Computed in constant prices, the gross national product rose from a level of 39.8 billion yen in the fiscal year beginning with April 1940, to only 41 billion yen in the fiscal year 1942. That this was due to an inadequate realization of requirements and inadequate planning, and not to the inherent limitations of the Japanese economy, is clear from the expansion that was secured after 1942. In the fiscal year 1943, the gross national product rose to 45.4 billion yen, and in 1944 to 50 billion yen.
The share of the gross national product devoted to direct war and munitions expenditures increased from 23 percent in 1941 to 31 percent in 1942, 42 percent in 1943 and 52 percent in 1944. In 1944, half of the remaining national product was accounted for by food. In 1943, however, the United States was devoting 45 percent of its vastly greater national product to direct war purposes. By the summer of 1944, the Japanese had exhausted the possibility of forcing a greater share of their economy into direct war activities. Their plants, railroad and mines were being, and had been for some time, under-maintained to a point where breakdowns were becoming more and more serious. The civilian population was underfed, was receiving practically no new clothing or miscellaneous civilian supplies, and was being worked to a degree of fatigue which was reflected in rising rates of absenteeism.
By 1944, Japan had increased ingot steel capacity to 225 percent of the 1937 capacity. A shortage of raw materials, however, which began with the United States embargo on scrap iron exports in July 1941 and was never overcome, prevented the operation of Japanese steel mills at anything approaching capacity. Japanese coal would not produce satisfactory metallurgical coke without the admixture of stronger continental coking coal; domestic iron ore was both limited in quantity and of lower grade than imported ores. The combination of limited quantities of high grade imported raw materials and lower grade domestic materials held production of ingot steel in the home islands to 6,800,000 tons in 1941, to a peak of 7,800,000 tons in 1943, and caused it to decline to 5,900,000 tons in 1944. This compared with a 1937 production of 5,800,000 tons and a theoretical capacity, using high-grade materials, of 13,600,000 tons in 1944. By the middle of 1i944, the increasing stringency of shipping and the interdiction of many of Japan's shipping routes had reduced coal and ore imports by two-thirds. Stockpiles of imported materials had already been heavily eaten into, and ingot steel production began to decline rapidly. In March 1945, imports of coal virtually ceased, and iron ore was cut off entirely, as the Japanese elected to devote their remaining shipping capacity to the hauling of vitally needed foodstuffs and salt. It is estimated by the Survey that, using only domestic raw materials, the Japanese steel industry could not have maintained a rate of production of ingot steel in excess of 1,500,000 tons per annum. By August 1945, the rate of output was still somewhat in excess of this
figure, but would soon have been reduced. The decline in Japan's steel production can be attributed to its dependence on shipping and the destruction of that shipping. Had this industry not been mortally wounded by shipping attack and had its destruction by bombing been called for, the effectiveness of the few strategic bombing attacks directed against the steel industry indicates that destruction of the principal plants by bombing or paralysis of the industry by disruption of railroad transportation would have been possible, but only at a later date.
The steel shortage constituted an over-all limitation on the war potential of the Japanese economy. Japanese planners were, however, able to secure very substantial increases in the production of those military products which the experiences of the war had demonstrated to be of outstanding importance. Aircraft production of all types, including training planes, was stepped up from 700 planes per month in the summer of 1942 to 2,572 planes in September 1944. Aircraft engine production was not only increased correspondingly in numbers, but average horsepower was doubled. Aircraft and antiaircraft gun and ammunition production was expanded tenfold. Radar and communications equipment was stepped up fivefold. The most important consumer of steel was the shipbuilding industry. The increasingly critical nature of Japan's shipping situation caused her to expand her naval and merchant shipbuilding programs to a point where 35 percent of all steel consumed was being used in that industry alone. Construction of merchant ships increased from approximately 238,000 tons in 1941, to 1,600,000 tons of steel ships and 254,000 tons of wooden ships in 1944. During 1942, warship deliveries included one battleship of 64,000 tons and six small carriers totalling 84,000 tons. In 1944, no battleships, but four aircraft carriers of 114,500 displacement tons and 141,300 tons of escort vessels and submarines were delivered. The increases in production of high-priority items involved the scaling down of steel availability for lower priority items, such as tanks, larger caliber guns and trucks, and the almost complete elimination of steel for civilian requirements, construction, or export.
During 1944, the effects of the net loss of shipping and slow-down in ship operations became such that by the end of the year it no longer was possible to protect even high-priority war production by further shifting of allocations of scarce materials from items of lesser priority. In addition to steel, other basic elements of the economy were involved. Oil, although not as important as steel in its broad impact on the remainder of the economy, was of critical importance to Japan's military machine and to her merchant marine. Oil imports from the south began declining in August 1943, and had been eliminated by April 1945. Crude oil stocks were virtually exhausted; refinery operations had to be curtailed; and stocks of aviation gasoline fell to less than 1,500,000 barrels, a point so low as to require a drastic cut in the pilot-training program and even in combat air missions. Bauxite imports declined from 136,000 tons in the second quarter of 1944, to 30,000 tons in the third, and stockpiles were only 3,000 tons. Stockpiles and the time delay between the various stages of production cushioned for a time the inevitable effects of the blockade on finished munitions production, but by November 1944, the over-all level of Japanese war production had begun to turn down, including even the highest priority items, such as aircraft engines.
It is the opinion of the Survey that by August 1945, even without direct air attack on her cities and industries, the over-all level of Japanese war production would have declined below the peak levels of 1944 by 40 to 50 percent solely as a result of the interdiction of overseas imports.
By mid-1944 those Japanese in possession of the basic information saw with reasonable clarity the economic disaster which was inevitably descending on Japan. Furthermore, they were aware of the disastrous impact of long-range bombing on Germany, and, with the loss of the Marianas, could foresee a similar attack on Japan's industries and cities. Their influence, however, was not sufficient to overcome the influence of the Army which was confident of its ability to resist invasion.
to which it would weaken enemy capability and will to resist our amphibious forces at the time of landings. This led, originally, to somewhat greater emphasis on the selection of targets such as aircraft factories, arsenals, electronics plants, oil refineries, and finished military goods, destruction of which could be expected to weaken the capabilities of the Japanese armed forces to resist at the Kyushu beachheads in November 1945, than on the disruption of the more basic elements of Japan's social, economic, and political fabric. Certain of the United States commanders and the representatives of the Survey who were called back from their investigations in Germany in early June 1945 for consultation stated their belief that, by the coordinated impact of blockade and direct air attack, Japan could be forced to surrender without invasion. The controlling opinion, however, was that any estimate of the effects of bombing on the Japanese social fabric and on the political decisions of those in control of Japan was bound to be so uncertain that target selection could safely be made only on the assumption that ground force invasion would be necessary to force capitulation.
With the benefit of hindsight, it appears that the twin objectives of surrender without invasion and reduction of Japan's capacity and will to resist an invasion, should the first not succeed, called for basically the same type of attack. Japan had been critically wounded by military defeats, destruction of the bulk of her merchant fleet, and almost complete blockade. The proper target, after an initial attack on aircraft engine plants, either to bring overwhelming pressure on her to surrender, or to reduce her capability of resisting invasion, was the basic economic and social fabric of the country. Disruption of her railroad and transportation system by daylight attacks, coupled with destruction of her cities by night and bad weather attacks, would have applied maximum pressure in support of either aim. This point of view was finally adopted. Although urban area attacks were initiated in force in March 1945, the railroad attack was just getting under way when the war ended.
The total tonnage of bombs dropped by Allied planes in the Pacific war was 656,400. Of this, 160,800 tons, or 24 percent, were dropped on the home islands of Japan. Navy aircraft accounted for 6,800 tons, Army aircraft other than B-29s for 7,000 tons, and the B-29s for 147,000 tons. By contrast, the total bomb tonnage in the European theater was 2,700,000 tons of which 1,360,000 tons were dropped within Germany's own borders.
Approximately 800 tons of bombs were dropped by China-based B-29s on Japanese home island targets from June 1944 to January 1945. These raids were of insufficient weight and accuracy to produce significant results.
By the end of November 1944, 4 months after seizure of the islands, the first of the long-range bomber bases in the Marianas became operational. The number of planes originally available was small and opposition was significant. Losses on combat missions averaged 3.6 percent. The tonnage dropped prior to 9 March 1945 aggregated only 7,180 tons although increasing month by month. The planes bombed from approximately 30,000 feet and the percentage of bombs dropped which hit the target areas averaged less than 10 percent. Nevertheless, the effects of even the relatively small tonnage hitting the selected targets were substantial. During this period, attacks were directed almost exclusively against aircraft, primarily aircraft engine, targets. The principal aircraft engine plants were hit sufficiently heavily and persistently to convince the Japanese that these plants would inevitably be totally destroyed. The Japanese were thereby forced into a wholesale and hasty dispersal program. The continuing pressure of immediate military requirements for more and more planes during the campaigns in the Pacific had prevented any earlier moves to disperse. When dispersal could no longer be avoided, the necessary underground tunnels, dispersed buildings, and accessory facilities such as roads, railroad spurs and power connections were not ready. As a result the decline in aircraft engine production, which shortages in special steels requiring cobalt, nickel and chrome had initiated in mid-1944, became precipitous.
On 9 March 1945, a basic revision in the method of B-29 attack was instituted. It was decided to bomb the four principal Japanese cities at night from altitudes averaging 7,000 feet. Japanese weakness in night fighters and antiaircraft made this program feasible. Incendiaries were used instead of high-explosive bombs and the lower altitude permitted a substantial increase in bomb load per plane. One thousand six hundred and sixty-seven tons of bombs were dropped on Tokyo in the first attack. The chosen areas were saturated. Fifteen square miles of Tokyo's most densely populated
area were burned to the ground. The weight and intensity of this attack caught the Japanese by surprise. No subsequent urban area attack was equally destructive. Two days later, an attack of similar magnitude on Nagoya destroyed 2 square miles. In a period of 10 days starting 9 March, a total of 1,595 sorties delivered 9,373 tons of bombs against Tokyo, Nagoya, Osake, and Kobe destroying 31 square miles of those cities at a cost of 22 airplanes. The generally destructive effect of incendiary attacks against Japanese cities had been demonstrated.
Thereafter, urban area attacks alternated with visual and radar attacks against selected industrial or military targets. In April, an extensive program of sowing minefields in channels and harbors at night was added. In the aggregate, 104,000 tons of bombs were directed at 66 urban areas; 14,150 tons were directed at aircraft factories; 10,600 tons at oil refineries; 4,708 at arsenals; 3,500 tons at miscellaneous industrial targets; 8,115 tons at air fields and sea-plane bases in support of the Okinawa operation; and 12,034 mines were sown.
Bombing altitudes after 9 March 1945 were lower, in both day and night attacks. Japanese opposition was not effective even at the lower altitudes, and the percentage of losses to enemy action declined as the number of attacking planes increased. Bomb loads increased and operating losses declined in part due to less strain on engines at lower altitudes. Bombing accuracy increased substantially, and averaged 35 to 40 percent within 1,000 feet of the aiming point in daylight attacks from 20,000 feet or lower.
Monthly tonnage dropped increased from 13,800 tons in March to 42,700 tons in July, and, with the activation of the Eighth Air Force on Okinawa, would have continued to increase thereafter to a planned figure of 115,000 tons per month, had the war not come to an end.
Three-quarters of the 6,740 tons of bombs dropped by carrier planes on the Japanese home islands were directed against airfields, warships, and miscellaneous military targets, and one-quarter against merchant shipping and other economic targets. Most of the warships sunk in home ports had already been immobilized for lack of fuel. The accuracy of low-level carrier plane attack was high, being at least 50 percent hits within 250 feet of the aiming point. The attack against the Hakodate-Aomori rail ferries in July 1945 sank or damaged all twelve of the ferries, 17 steel ships, and 149 smaller ships.
The railroad system had not yet been subjected to substantial attack and remained in reasonably good operating condition at the time of surrender. Little damage was suffered which interfered with main line operations. Trains were running through Hiroshima 48 hours after the dropping of the atomic bomb on that city. Damage to local transport facilities, however, seriously disrupted the movement of supplies within and between cities, thereby hindering production, repair work and dispersal operations.
Japan's electric power system was properly rejected for specific attack because of the large number of small targets presented. Urban incendiary attacks destroyed the electric distribution systems in the burned-out areas simultaneously with the consumer load previously served by them. The hydro-electric generating plants and the transmission networks survived without substantial damage. Twenty-six urban steam-generating plants were damaged as an incident to other attacks, the aggregate loss of capacity being less than one-seventh of Japan's total generating capacity. The urban area incendiary attacks eliminated
completely the residential and smaller commercial and industrial structures in the affected areas and a significant number of important plants, but a portion of the more substantially constructed office buildings and factories in those areas and the underground utilities survived. By 1944 the Japanese had almost eliminated home industry in their war economy. They still relied, however, on plants employing less than 250 workers for subcontracted parts and equipment. Many of these smaller plants were concentrated in Tokyo and accounted for 50 percent of the total industrial output of the city. Such plants suffered severe damage in urban incendiary attacks.
Four hundred and seventy thousand barrels of oil and oil products, 221,000 tons of foodstuffs and 2 billion square yards of textiles were destroyed by air attacks. Ninety-seven percent of Japan's stocks of guns, shells, explosives, and other military supplies were thoroughly protected in dispersed or underground storage depots, and were not vulnerable to air attack.
Physical damage to plant installations by either area or precision attacks, plus decreases due to dispersal forced by the threat of further physical damage, reduced physical productive capacity by roughly the following percentages of pre-attack plant capacity: oil refineries, 83 percent; aircraft engine plants, 75 percent; air-frame plants, 60 percent; electronics and communication equipment plants, 70 percent; army ordnance plants, 30 percent; naval ordnance plants, 28 percent; merchant and naval shipyards, 15 percent; light metals, 35 percent; ingot steel, 15 percent; chemicals, 10 percent.
The economic consequences of the physical damage wrought by air attack are closely interrelated with the concurrent effects of the interdiction of imports, the cumulative effects of under-maintenance of plants, and the declining health, vigor and determination of the Japanese people.
Let us first consider the level of Japanese industrial activity in July 1945, the last full month before surrender. Electric power and coal consumption were both almost exactly 50 percent of the peak reached in 1944. Production efficiency had, however, declined and the overall industrial output was approximately 40 percent of the 1944 peak. Output varied considerably as between industries, hit and unhit plants, and by areas. Output of air frame was 40 percent of the 1944 peak; aircraft engines, 25 percent; shipbuilding, 25 percent; army ordnance, 45 percent; and naval ordnance, 43 percent. Oil refining had declined to less than 15 percent of the 1943 output. Primary aluminum production was 9 percent of the 1944 peak. Although nitric acid production had declined to about 17 percent of the 1944 peak, explosives production was about 45 percent of the 1944 figure.
In each one of these industries, the occasion for the decline appears to have been different. Electric power consumption fell, not because more power was not available, but because demand had declined. Coal supply was primarily limited by the decline in inter-island shipping from Hokkaido and Kyushu, and the inability of the railroad system completely to fill the gap. Despite a decline in demand, shortages of coal were universal throughout the economy. Airframe production was limited primarily by the continuing effects of the dispersal program brought on by the initial bombing, and aggravated by the subsequent destruction of numerous plants prior to completion of dispersal. Had the level of production been any higher, however, aluminum stocks would have been exhausted and aluminum would have become the controlling bottleneck. In any event, not enough aircraft engines were being produced to equip the airframes. Aircraft engine production was plagued by shortages of special steels, but in July 1945, plant damage and delay in completing the underground and dispersed plants started in the spring of the year temporarily prevented the full use of the small stocks of such steels available at the time. Output of radar and radio equipment was limited by plant capacity, the small factories supplying parts having been destroyed in the Tokyo city raids and many of the larger plants either destroyed or forced to disperse. Shipbuilding and heavy ordnance production were limited by the availability of steel. Oil refineries, aluminum plants and steel plants were basically limited by lack of foreign raw materials. Explosive plants were still using up inventories of nitric acid but would shortly have had to adjust their output to the current availability of nitric acid.
The Japanese labor force had declined in efficiency due to malnutrition and fatigue, the destruction of much of the urban housing and the difficulties of local transportation. Production
hours lost through all causes including absenteeism, sickness, air-raid alerts and enforced idleness rose from 20 percent in 1944 to over 40 percent in July 1945. The size of the labor force employed did not materially decline and the productive hours actually worked remained sufficiently high to indicate that such influence as manpower deficiencies may have had on the over-all level of production in July 1945, was largely ascribable to the continued drafting of highly skilled workers into the armed services and to the inefficient administration of manpower in meeting the rapidly shifting requirements resulting from bombing, rather than to over-all lack of labor.
A Survey investigation of production in plants employing more than 50 employees in 39 representative cities of Japan indicates that production in those plants which suffered any direct physical damage dropped off by July 1945, to 27 percent of peak output in 1944, while production in the undamaged plants fell off to 54 percent. Production in all plants in the sample, including both hit and unhit, dropped to 35 percent of peak by July 1945. It appears probable that the indirect effects of the urban raids through increased absenteeism, disruption of supply lines and administrative confusion fully compensate for diversions of manpower and material from hit to unhit plants. The difference between 54 percent, being the rate of production in unhit plants, and 35 percent, being the average for all plants, is, therefore, a conservative indication of the impact of air attacks, both urban and precision, on production in these cities.
Even though the urban area attacks and attacks on specific industrial plants contributed a substantial percentage to the over-all decline in Japan's economy, in many segments of that economy their effects were duplicative. Most of the oil refineries were out of oil, the alumina plants out of bauxite, the steel mills lacking in ore and coke, and the munitions plants low in steel and aluminum. Japan's economy was in large measure being destroyed twice over, once by cutting off of imports, and secondly by air attack. A further tightening of Japan's shipping situation, so as to eliminate remaining imports from Korea and coastwise and inter-island shipping, coupled with an attack on Japan's extremely vulnerable railroad network, would have extended and cumulated the effects of the shipping attack already made.
Much of Japan's coastal and inter-island traffic had already been forced on to her inadequate railroads. The principal coal mines of Japan are located on Kyushu and Hokkaido. This coal traffic, formerly water borne, was moving by railroads employing the Kanmon tunnels and the Hakkodate-Aomori rail ferry. The railroads on Honshu include few main lines and these lines traverse bridges of considerable vulnerability. Japan is largely a mountainous country lacking automobile roads, trucks or the gasoline to make use of them. A successful attack on the Hakkodate rail ferry, the Kanmon tunnels and 19 bridges and vulnerable sections of line so selected as to set up five separate zones of complete interdiction would have virtually eliminated further coal movements, would have immobilized the remainder of the rail system through lack of coal, and would have completed the strangulation of Japan's economy. This strangulation would have more effectively and efficiently destroyed the economic structure of the country than individually destroying Japan's cities and factories. It would have reduced Japan to a series of isolated communities, incapable of any sustained industrial production, incapable of moving food from the agricultural areas to the cities, and incapable of rapid large-scale movements of troops and munitions.
The Survey believes that such an attack, had it been well-planned in advance, might have been initiated by carrier-based attacks on shipping and on the Hakkodate ferry in August 1944, could have been continued by aerial mining of inland waterways beginning in December 1944, and could have been further continued by initiating the railroad attack as early as April 1945. The Survey has estimated that force requirements to effect complete interdiction of the railroad system would have been 650 B-29 visual sorties carrying 5,200 tons of high explosive bombs. Monthly tonnages equal to one and one-half times that required to effect the original interdiction should have been sufficient, in view of the Japanese lack of preparation and slowness in effecting repairs, to maintain the interdiction by destroying such bridges and other facilities as the Japanese were able to repair. The use of Azon guided bombs, which could have been made available at that time, would have greatly increased accuracy against targets of this type and reduced force requirements to approximately one-sixth of those given above. An integrated
program employing both carrier planes and B-29s would have capitalized on the differing operational capabilities of each.
The economic effects of the transportation attack would have had a direct impact on the Japanese people and on their determination to continue the war. In order to bring maximum pressure on the civilian population and to complicate further the Japanese economic problems, night and bad weather attacks on urban areas could have been carried out simultaneously with the transportation attack. One of the important factors inducing Japan's leaders to accept unconditional surrender was a realization that the Japanese armed forces had lost their ability to protect the people and that under the impact of direct air attack and lowered livelihood their confidence in victory and determination to continue the war were rapidly declining.
The Japanese had constructed extensive firebreaks by tearing down all houses along selected streets or natural barriers. The total number of buildings torn down in this program, as reported by the Japanese, amounted to 615,000 as against 2,510,000 destroyed by the air attacks themselves. These firebreaks did not effectively stop the spread of fire, as incendiaries were dropped on both sides of the breaks. They did, however, constitute avenues of escape for the civilian population.
The Japanese instituted a civilian-defense organization prior to the war. It was not until the summer of 1944, however, that effective steps were taken to reduce the vulnerability of Japan's civilian population to air attacks. By that time, the shortage of steel, concrete and other construction materials was such that adequate air-raid shelters could no longer be built. Each family was given the obligation of providing itself with some kind of an excavation covered with bamboo and a little dirt. In addition, tunnels were dug into the sides of hills wherever the topography permitted.
Japanese planning and the means for carrying out the plans were thus deficient for a first-class civilian defense program. In spite of these limitations, such civilian defense measures as they were able to put through contributed substantially in minimizing casualties. School children and other nonessential urban dwellers were evacuated to the country. Those who remained were organized to combat fires and to provide mutual assistance. The air raid warning system was generally efficient. The weight of the individual attacks was, however, far heavier than the Japanese had envisaged or were able to cope with. In the major fire attacks, the civilian defense organizations were simply overwhelmed.
The growing food shortage was the principal factor affecting the health and vigor of the Japanese people. Prior to Pearl Harbor the average per capita caloric intake of the Japanese people was about 2,000 calories as against 3,400 in the United States. The acreage of arable land in Japan is only 3 percent of that of the United States to support a population over half as large. In order to provide the prewar diet, this arable acreage was more intensively cultivated, using more manpower and larger quantities of fertilizer than in any other country in the world; fishing was developed into a major industry; and rice, soybeans and other foodstuffs amounting to 19 percent of the caloric intake were imported. Despite the rationing of food beginning in April 1941 the food situation became critical. As the war progressed, imports became more and more difficult, the waters available to the fishing fleet and the ships and fuel oil for its use became increasingly restricted. Domestic food production itself was affected by the drafting of the younger males and by an increasing shortage of fertilizers.
By 1944, the average per capita caloric intake had declined to approximately 1,900 calories. By the summer of 1945 it was about 1,680 calories per
capita. Coal miners and heavy industrial workers received higher-than-average rations, the remaining populace, less. The average diet suffered even more drastically from reductions in fats, vitamins and minerals required for balance and adversely affected rates of recovery and mortality from disease and bomb injuries.
Undernourishment produced a major increase in the incidence of beriberi and tuberculosis. It also had an important effect on the efficiency and morale of the people, and contributed to absenteeism among workers.
Survey interrogation of a scientifically designed cross-section sample of the Japanese civilian population revealed a high degree of uniformity as between city and rural sectors of the population and as between various economic and social strata in their psychological reaction to the war. A uniformly high percentage considered Japan's greatest weaknesses to have been in the material realm, either lack of resources, productive plant or modern weapons, and her greatest strength to have been in the Yamato spirit of the Japanese people, their willingness to make every personal sacrifice, including that of life itself, for the Emperor or Japan.
The Japanese people reacted to news of the attack against the United States and its Allies with mingled feelings of fear, insecurity and hope. To a people wearied by 10 years of war in China, it was clear that this would be a major war and not an "incident". The early Japanese military successes, particularly the capture of Singapore and the southern regions, were followed by a wave of optimism and high confidence. Subsequent defeats were studiously withheld from the people or disguised as strategic withdrawals. Prior to the loss of Saipan confidence in eventual victory remained high in spite of exhausting work, poor nutrition and rising black market prices. In June 1944 approximately two percent of the population believed that Japan faced the probability of defeat. The fall of Saipan could not be kept from the Japanese people. Even though the psychological effect of this disaster was far greater on the Japanese leaders and intellectuals than on the mass of the population, all indices of Japanese morale began thereafter to decline. By December 1944 air attacks from the Marianas against the home islands had begun, defeats in the Philippines had been suffered, and the food situation had deteriorated; 10 percent of the people believed Japan could not achieve victory. By March 1945, when the night incendiary attacks began and the food ration was reduced, this percentage had risen to 19 percent. In June it was 46 percent, and just prior to surrender, 68 percent. Of those who had come to this belief over one-half attributed the principal cause to air attacks, other than the atomic bombing attacks, and one-third to military defeats.
Sixty-four percent of the population stated that they had reached a point prior to surrender where they felt personally unable to go on with the war. Of these, less than one-tenth attributed the cause to military defeats, one-quarter attributed the cause to shortages of food and civilian supplies, the largest part to air attack.
A striking aspect of the air attack was the pervasiveness with which its impact on morale blanketed Japan. Roughly one-quarter of all people in cities fled or were evacuated, and these evacuees, who themselves were of singularly low morale, helped spread discouragement and disaffection for the war throughout the islands. This mass migration from the cities included an estimated 8,500,000 persons. Throughout the Japanese islands, whose people had always thought themselves remote from attack, United States planes crisscrossed the skies with no effective Japanese air or antiaircraft opposition. That this was an indication of impending defeat became as obvious to the rural as to the urban population.
Progressively lowered morale was characterized by loss of faith in both military and civilian leaders, loss of confidence in Japan's military might and increasing distrust of government news releases and propaganda. People became short-tempered and more outspoken in their criticism of the government, the war and affairs in general. Until the end, however, national traditions of obedience and conformity, reinforced by the police organization, remained effective in controlling the behavior of the population. The Emperor largely escaped the criticism which was directed at other leaders, and retained the people's faith in him. It is probable that most Japanese would have passively faced death in a continuation of the hopeless struggle, had the Emperor so ordered. When the Emperor announced the unconditional surrender the first reaction of the people was one of regret and surprise, followed shortly by relief.
The interrelation of military, economic and morale
factors was complex. To a certain extent each reacted on the other. In the final analysis the Japanese military machine had lost its purpose when it could no longer protect the Japanese people from destruction by air attack. General Takashima, when asked by the Survey as to his reaction to the Imperial Rescript, stated that surrender had become unavoidable; the Army, even should it repel invasion, could no longer protect the Japanese people from extermination.
Eyewitness accounts of the explosion all describe similar pictures. The bombs exploded with a tremendous flash of blue-white light, like a giant magnesium flare. The flash was of short duration and accompanied by intense glare and heat. It was followed by a tremendous pressure wave and the rumbling sound of the explosion. This sound is not clearly recollected by those who survived near the center of the explosion, although it was clearly heard by others as much as fifteen miles sway. A huge snow-white cloud shot rapidly into the sky and the scene on the ground was obscured first by a bluish haze and then by a purple-brown cloud of dust and smoke.
Such eyewitness accounts reveal the sequence of events. At the time of the explosion, energy was given off in the forms of light, heat, radiation, and pressure. The complete band of radiations, from X- and gamma-rays, through ultraviolet and light rays to the radiant heat of infra-red rays, travelled with the speed of light. The shock wave created by the enormous pressures built up almost instantaneously at the point of explosion but moved out more slowly, that is at about the speed of sound. The superheated gases constituting the original fire ball expanded outward and upward at a slower rate.
The light and radiant heat rays accompanying the flash travelled in a straight line and any opaque object, even a single leaf of a vine, shielded objects lying behind it. The duration of the flash was only a fraction of a second, but it was sufficiently intense to cause third degree burns to exposed human skin up to a distance of a mile. Clothing ignited, though it could be quickly beaten out, telephone poles charred, thatchroofed houses caught fire. Black or other dark-colored surfaces of combustible material absorbed the heat and immediately charred or burst into flames; white or light-colored surfaces reflected a substantial portion of the rays and were not consumed. Heavy black clay tiles which are an almost universal feature of the roofs of Japanese houses bubbled at distances up to a mile. Test of samples of this tile by the National Bureau of Standards in Washington indicates that temperatures in excess of 1,800° C. must have been generated in the surface of the tile to produce such an effect. The surfaces of granite blocks exposed to the flash scarred and spalled at distances up to almost a mile. In the immediate area of ground zero (the point on the ground immediately below the explosion), the heat charred corpses beyond recognition.
Penetrating rays such as gamma-rays exposed X-ray films stored in the basement of a concrete hospital almost a mile from ground zero. Symptoms of their effect on human beings close to the center of the explosion, who survived other effects thereof, were generally delayed for two or three days. The bone marrow and as a result the process of blood formation were affected. The white corpuscle count went down and the human processes of resisting infection were destroyed. Death generally followed shortly thereafter.
The majority of radiation cases who were at greater distances did not show severe symptoms until 1 to 4 weeks after the explosion. The first symptoms were loss of appetite, lassitude and general discomfort. Within 12 to 48 hours, fever became evident in many cases, going as high as 104° to 105° F., which in fatal cases continued until death. If the fever subsided, the patient usually
showed a rapid disappearance of other symptoms and soon regained his feeling of good health. Other symptoms were loss of white blood corpuscles, loss of hair, and decrease in sperm count.
Even though rays of this nature have great powers of penetration, intervening substances filter out portions of them. As the weight of the intervening material increases the percentage of the rays penetrating goes down. It appears that a few feet of concrete, or a somewhat greater thickness of earth, furnished sufficient protection to humans, even those close to ground zero, to prevent serious after effects from radiation.
The blast wave which followed the flash was of sufficient force to press in the roofs of reinforced concrete structures and to flatten completely all less sturdy structures. Due to the height of the explosion, the peak pressure of the wave at ground zero was no higher than that produced by a near miss of a high-explosive bomb, and decreased at greater distances from ground zero. Reflection and shielding by intervening hills and structures produced some unevenness in the pattern. The blast wave, however, was of far greater extent and duration than that of a high-explosive bomb and most reinforced-concrete structures suffered structural damage or collapse up to 700 feet at Hiroshima and 2,000 feet at Nagasaki. Brick buildings were flattened up to 7,300 feet at Hiroshima and 8,500 feet at Nagasaki. Typical Japanese houses of wood construction suffered total collapse up to approximately 7,300 feet at Hiroshima and 8,200 feet at Nagasaki. Beyond these distances structures received less serious damage to roofs, wall partitions, and the like. Glass windows were blown out at distances up to 5 miles. The blast wave, being of longer duration than that caused by high-explosive detonations, was accompanied by more flying debris. Window frames, doors, and partitions which would have been shaken down by a near-miss of a high-explosive bomb were hurled at high velocity through those buildings which did not collapse. Machine tools and most other production equipment in industrial plants were not directly damaged by the blast wave, but were damaged by collapsing buildings or ensuing general fires.
The above description mentions all the categories of the destructive action by the atomic-bomb explosions at Hiroshima and Nagasaki. There were no other types of action. Nothing was vaporized or disintegrated; vegetation is growing again immediately under the center of the explosions; there are no indications that radio-activity continued after the explosion to a sufficient degree to harm human beings.
Let us consider, however, the effect of these various types of destructive action on the cities of Hiroshima, and Nagasaki and their inhabitants.
Hiroshima is built on a broad river delta; it is flat and little above sea level. The total city area is 26 square miles but only 7 square miles at the center were densely built up. The principal industries, which had been greatly expanded during the war, were located on the periphery of the city. The population of the city had been reduced from approximately 340,000 to 245,000 as a result of a civilian defense evacuation program. The explosion caught the city by surprise. An alert had been sounded but in view of the small number of planes the all-clear had been given. Consequently, the population had not taken shelter. The bomb exploded a little northwest of the center of the built-up area. Everyone who was out in the open and was exposed to the initial flash suffered serious burns where not protected by clothing. Over 4 square miles in the center of the city were flattened to the ground with the exception of some 50 reinforced concrete buildings, most of which were internally gutted and many of which suffered structural damage. Most of the people in the flattened area were crushed or pinned down by the collapsing buildings or flying debris. Shortly thereafter, numerous fires started, a few from the direct heat of the dash, but most from overturned charcoal cooking stoves or other secondary causes. These fires grew in size, merging into a general conflagration fanned by a wind sucked into the center of the city by the rising heat. The civilian-defense organization was overwhelmed by the completeness of the destruction, and the spread of fire was halted more by the air rushing toward the center of the conflagration than by efforts of the fire-fighting organization.
Approximately 60,000 to 70,000 people were killed, and 50,000 were injured. Of approximately 90,000 buildings in the city, 65,000 were rendered unusable and almost all the remainder received at least light superficial damage. The underground utilities of the city were undamaged except where they crossed bridges over the rivers cutting through the city. All of the small factories in the
center of the city were destroyed. However, the big plants on the periphery of the city were almost completely undamaged and 94 percent of their workers unhurt. These factories accounted for 74 percent of the industrial production of the city. It is estimated that they could have resumed substantially normal production within 30 days of the bombing, had the war continued. The railroads running through the city were repaired for the resumption of through traffic on 8 August, 2 days after the attack.
Nagasaki was a highly congested city built around the harbor and up into the ravines and river valleys of the surrounding hills. Spurs of these hills coming down close to the head of the bay divide the city roughly into two basins. The built-up area was 3.4 square miles of which 0.6 square miles was given over to industry. The peak wartime population of 285,000 had been reduced to around 230,00 by August 1945, largely by pre-raid evacuations. Nagasaki had been attacked sporadically prior to 9 August by an aggregate of 136 planes which dropped 270 tons of high explosives and 53 tons of incendiary bombs. Some 2 percent of the residential buildings had been destroyed or badly damaged; three of the large industrial plants had received scattered damage. The city was thus comparatively intact at the time of the atomic bombing.
The alarm was improperly given and therefore few persons were in shelters. The bomb exploded over the northwest portion of the city; the intervening hills protected a major portion of the city lying in the adjoining valley. The heat radiation and blast actions of the Nagasaki bomb were more intense than those of the bomb dropped over Hiroshima. Reinforced-concrete structures were structurally damaged at greater distances; the heavy steel-frame industrial buildings of the Mitsubishi steel works and the arms plant were pushed at crazy angles away from the center of the explosion. Contrary to the situation at Hiroshima, the majority of the fires that started immediately after the explosion resulted from direct ignition by the flash.
Approximately 40,000 persons were killed or missing and a like number injured. Of the 52,000 residential buildings in Nagasaki 14,000 were totally destroyed and a further 5,400 badly damaged. Ninety-six percent of the industrial output of Nagasaki was concentrated in the large plants of the Mitsubishi Co. which completely dominated the town. The arms plant and the steel works were located within the area of primary damage. It is estimated that 58 percent of the yen value of the arms plant and 78 percent of the value of the steel works were destroyed. The main plant of the Mitsubishi electric works was on the periphery of the area of greatest destruction. Approximately 25 percent of its value was destroyed. The dockyard, the largest industrial establishment in Nagasaki and one of the three plants previously damaged by high-explosive bombs, was located down the bay from the explosion. It suffered virtually no new damage. The Mitsubishi plants were all operating, prior to the attack, at a fraction of their capacity because of a shortage of raw materials. Had the war continued, and had the raw material situation been such as to warrant their restoration, it is estimated that the dockyard could have been in a position to produce at 80 percent of its full capacity within 3 to 4 months; that the steel works would. have required a year to get into substantial production; that the electric works could have resumed some production within 2 months and been back at capacity within 6 months; and that restoration of the arms plant to 60 to 70 percent of former capacity would have required 15 months.
Some 400 persons were in the tunnel shelters in Nagasaki at the time of the explosion. The shelters consisted of rough tunnels dug horizontally into the sides of hills with crude, earth-filled blast walls protecting the entrances. The blast walls were blown in but all the occupants back from the entrances survived, even in those tunnels almost directly under the explosion. Those not in a direct line with the entrance were uninjured. The tunnels had a capacity of roughly 100,000 persons. Had the proper alarm been sounded, and these tunnel shelters been filled to capacity, the loss of life in Nagasaki would have been substantially lower.
The Survey has estimated that the damage and casualties caused at Hiroshima by the one atomic bomb dropped from a single plane would have required 220 B-29s carrying 1,200 tons of incendiary bombs, 400 tons of high-explosive bombs, and 500 tons of anti-personnel fragmentation bombs, if conventional weapons, rather than an atomic bomb, had been used. One hundred and twenty-five B-29s carrying 1,200 tons of bombs
would have been required to approximate the damage and casualties at Nagasaki. This estimate pre-supposed bombing under conditions similar to those existing when the atomic bombs were dropped and bombing accuracy equal to the average attained by the Twentieth Air Force during the last 3 months of the war.
As might be expected, the primary reaction of the populace to the bomb was fear, uncontrolled terror, strengthened by the sheer horror of the destruction and suffering witnessed and experienced by the survivors. Prior to the dropping of the atomic bombs, the people of the two cities had fewer misgivings about the war than people in other cities and their morale held up after it better than might have been expected. Twenty-nine percent of the survivors interrogated indicated that after the atomic bomb was dropped they were convinced that victory for Japan was impossible. Twenty-four percent stated that because of the bomb they felt personally unable to carry on with the war. Some 40 percent testified to various degrees of defeatism. A greater number (24 percent) expressed themselves as being impressed with the power and scientific skill which underlay the discovery and production of the atomic bomb than expressed anger at its use (20 percent). In many instances, the reaction was one of resignation.
The effect of the atomic bomb on the confidence of the Japanese civilian population outside the two cities was more restricted. This was in part due to the effect of distance, lack of understanding of the nature of atomic energy, and the impact of other demoralizing experiences. The role of the atomic bomb in the surrender must be considered along with all the other forces which bore upon that question with Japan.
The first definitive break in the political coalition which began the war occurred following our success at Saipan. Ten days thereafter, on 16 July 1944, the cabinet headed by General Tojo fell. This significant turn in the course of Japan's wartime politics was not merely the result of an immediate crisis. Even at that date, elements opposing continuation of the war had found means of applying pressure against the fanatic exponents of Japan's militaristic clique. The original factions who had either opposed war before Pearl Harbor, or gone along, or "retired" in the first phase of the conflict recognized as early as the spring of 1944 that Japan was facing ultimate defeat. By that time, United States determination to fight and her ability to mount over-powering offensives in the Pacific, even before the opening of the European Second Front, had already been demonstrated to many of those who had access to all the facts. The political problem of those who saw the situation was to circulate among other leaders in retirement or outside the government a true picture of the war and then unseat the Tojo government in favor of one which would bring the war to an end.
Rear Admiral Takagi of the Navy General Staff made a study between 20 September 1943 and February 1944, of the war's battle lessons up to that time. Based on analysis of air, fleet and merchant ship losses, Japan's inability to import essential materials for production, and the potentiality of air attacks on the home islands, Takagi concluded that Japan could not win and should seek a compromise peace. His study and a similar one made by Sakomizu of the Cabinet Planning Board documented the fears of the Jushin, and through them of Marquis Kido, that all was not well with Tojo's prosecution of the
war. With the loss of Saipan, it was possible to build up sufficient pressure to force Tojo's retirement.
The government of General Koiso, who was chosen by the ever-cautious Kido to head the succeeding cabinet, did not have the strength to stand up to the military and was a disappointment to the more enthusiastic peace makers. In spite of original instructions to give "fundamental reconsideration" to the problem of continuing the war, his only accomplishment in that direction was the creation of a Supreme War Direction Council, an inner cabinet which supplied the mechanism through which the problem of surrender was eventually resolved.
The conviction and strength of the peace party was increased by the continuing Japanese military defeats, and by Japan's helplessness in defending itself against the ever-growing weight of air attack on the home islands. On 7 April 1945, less than a week after United States landings on Okinawa, Koiso was removed and Marquis Kido installed Admiral Suzuki as premier. Kido testified to the Survey that, in his opinion, Suzuki alone had the deep conviction and personal courage to stand up to the military and bring the war to an end.
Early in May 1945, the Supreme War Direction Council began active discussion of ways and means to end the war, and talks were initiated with Soviet Russia seeking her intercession as mediator.
The talks by the Japanese ambassador in Moscow and with the Soviet ambassador in Tokyo did not make progress. On 20 June the Emperor, on his own initiative, called the six members of the Supreme War Direction Council to a conference and said it was necessary to have a plan to close the war at once, as well as a plan to defend the home islands. The timing of the Potsdam Conference interfered with a plan to send Prince Konoye to Moscow as a special emissary with instructions from the cabinet to negotiate for peace on terms less than unconditional surrender, but with private instructions from the Emperor to secure peace at any price. Although the Supreme War Direction Council, in its deliberations on the Potsdam Declaration, was agreed on the advisability of ending the war, three of its members, the Prime Minister, the Foreign Minister and the Navy Minister, were prepared to accept unconditional surrender, while the other three, the Army Minister, and the Chiefs of Staff of both services, favored continued resistance unless certain mitigating conditions were obtained.
On 6 August the atomic bomb was dropped on Hiroshima, and on 9 August Russia entered the war. In the succeeding meetings of the Supreme War Direction Council, the differences of opinion previously existing as to the Potsdam terms persisted exactly as before. By using the urgency brought about through fear of further atomic bombing attacks, the Prime Minister found it possible to bring the Emperor directly into the discussions of the Potsdam terms. Hirohito, acting as arbiter, resolved the conflict in favor of unconditional surrender.
The public admission of defeat by the responsible Japanese leaders, which constituted the political objective of the United States offensive begun in 1943, was thus secured prior to invasion and while Japan was still possessed of some 2,000,000 troops and over 9,000 planes in the home islands. Military defeats in the air, at sea and on the land, destruction of shipping by submarines and by air, and direct air attack with conventional as well as atomic bombs, all contributed to this accomplishment.
There is little point in attempting precisely to impute Japan's unconditional surrender to any one of the numerous causes which jointly and cumulatively were responsible for Japan's disaster. The time lapse between military impotence and political acceptance of the inevitable might have been shorter had the political structure of Japan permitted a more rapid and decisive determination of national policies. Nevertheless, it seems clear that, even without the atomic bombing attacks, air supremacy over Japan could have exerted sufficient pressure to bring about unconditional surrender and obviate the need for invasion.
Based on a detailed investigation of all the facts, and supported by the testimony of the surviving Japanese leaders involved, it is the Survey's opinion that certainly prior to 31 December 1945, and in all probability prior to 1 November 1945, Japan would have surrendered even if the atomic bombs had not been dropped, even if Russia had not entered the war, and even if no invasion had been planned or contemplated.
Japan's geographical situation determined that the Pacific war should in large measure be a war for control of the sea, and to insure control of the sea, for control of the air over it. As a result, attacks against warships and merchant ships and amphibious operations for possession of island positions on which forward bases could be located were close to the heart of the struggle. Carrier task forces, surface ships to provide logistic support, and submarines therefore assumed roles of unusual importance.
Japan's industrial potential was approximately 10 percent of that of the United States. Even though her research and technical design work was not purely imitative, her ability to develop reliable operating equipment in the new fields was low. Her radar and communications equipment was weak. She could not build sufficient ships or escort vessels. She lacked construction equipment to build adequate airfields. She was always hampered by a lack of oil. Her antiaircraft was outmoded. She could not economically afford to build adequate shelters for her population. She could not both disperse her industry and also repair damaged plants. She chose dispersal rather than repair, but she had insufficient means even to disperse effectively.
1. Control of the air was essential to the success of every major military operation. Control of the air enabled surface vessels to sail the seas as far as that control extended, even within range of enemy land-based airplanes. Control of the air permitted amphibious landings at any point where that control could be assured. Control of the air permitted close air support to ground forces, the effectiveness of which was decisive wherever fully employed. Control of the air over lines of communications permitted effective interdiction of them to the enemy and preserved them to ourselves. Control of the air over the Japanese home islands permitted the destruction by long-range bombing of such of her industries and cities as we chose to attack. The first objective of all commanders in the Pacific war, whether ground, sea or air, whether American, Allied, or Japanese, was to assure control of the air.
2. Control of the air was not easily achieved, and involved the coordinated application of all the resources of the nation. Air power consisted not merely of the planes and pilots that engaged the enemy, but of all the sources of strength that supported, reinforced and exploited control of the air. It was coordinated teamplay of ground, sea and air forces, both ground-based and carrier-based, and their supporting services, backed up by the full effort of all phases of the home front that enabled us to secure control of the air, at first locally and then more generally, culminating in
virtual freedom of the skies over the Japanese home islands themselves.
3. The limitations of air control deserve special mention. It was never completely possible to deny the air to the enemy. It was considered that we had control of the air when the enemy could not operate in it without prohibitive losses in relation to results achieved, while our own planes could operate in it at will and with acceptable risk of loss. The Japanese increased their ratio of results achieved to losses by adopting Kamikaze tactics. This was a measure of desperation, but the results obtained were considerable and, had they been much greater, might have caused us to withdraw or to modify our strategic plans. The principle involved indicates the degree to which defensive air control must be improved or enemy bases kept beyond the range of enemy suicide planes or guided missiles from such land or sea as we propose to use.
4. Given air control, there were also limitations as to the specific results which could be achieved in exploiting such control by aircraft carrying conventional high-explosive bombs. Fox holes, underground emplacements and other prepared defenses could not in many cases be reduced, and it was necessary to eliminate remaining ground forces in costly close-range fighting even though these forces were isolated and completely cut off from supplies and reinforcements.
Weather and darkness limited exploitation of air control, but as the war progressed technical and tactical advances were made which progressively reduced these limitations.
Combat radius of fighters and time on patrol at maximum radius, although great by previously existing standards, required that airfields or carriers be available within 300 nautical miles or less of the critical areas of surface combat for optimum fighter cover. The effective radius of our longest range bombers was limited to 1,500 miles and bases still closer to Japan were considered essential for emergency landing and fighter support.
The importance of reducing these limitations of control of the air and its exploitation by the application of research and development work in postwar years is obvious.
5. The experience of the Pacific war supports the findings of the Survey in Europe that heavy, sustained and accurate attack against carefully selected targets is required to produce decisive results when attacking an enemy's sustaining resources. It further supports the findings in Germany that no nation can long survive the free exploitation of air weapons over its homeland. For the future it is important fully to grasp the fact that enemy planes enjoying control of the sky over one's head can be as disastrous to one's country as its occupation by physical invasion.
Prior to the European mar, we underestimated the predominant role that air power was to play and allocated to it too small a share of even the inadequate resources then available to the Army and Navy. At the outbreak of the Pacific war our deficiency was particularly great in modern land-based fighters and in carriers. One thousand planes in the Philippines, at least equal in performance to the best then available to the Japanese, including types effective against shipping, well-manned, equipped and supplied, and dispersed on some 50 airfields, would have seriously impeded the original Japanese advance if knowledge of their existence had not entirely dissuaded the Japanese from making the attempt. The loss of relatively antiquated battleships at Pearl Harbor had little effect on the Navy's combat capabilities at that time, while the addition of a few carriers would have enormously increased its capabilities. Larger overall appropriations to the armed forces, beginning at the time of Japanese occupation of Manchuria when the threat to peace in the Far East became evident, might have made war unnecessary and would have paid for itself many times over in reduced casualties and expenditures had war still been unavoidable.
Upon entering the war, we were deficient not only in numbers, but in quality of many of our aircraft types. We were forced thereafter into hasty and costly modification and technical development programs to raise the performance of our aircraft to acceptable standards. These programs could have been conducted more efficiently and economically during prewar years.
In the actual conduct of the war we more quickly grasped the strategic revolution brought about by the capabilities of air power than did the Japanese. By the end of 1943 we had achieved
through combat and the augmentation of our forces, such clear cut superiority over the Japanese in all elements of air power that eventual victory was assured.
In exploiting this superiority greater economy of effort was possible. The structure of our prewar military organization provided no means, short of the President, for integrating our armed forces. Under the pressure of war the Joint Chiefs of Staff was the most decisive mechanism then possible to fill this gap. Each of its members had in effect the power of veto and the required unanimity was produced by compromise. It proved impossible to agree on an overall commander for the Pacific as a whole. Our military and economic strength, however, made it possible to plan and execute a dual line of advance across the Pacific and to mount an air attack of sufficient weight to induce unconditional surrender concurrently with the preparation of a full scale invasion.
Capture of the Gilbert Islands produced limited strategic results. Attacks on Rabaul and other bypassed positions were continued longer and in greater volume than required. The effectiveness of high-level attack in softening up prepared defenses and in sinking maneuvering ships was overestimated. Prior to the occupation of the Marianas, B-29s could have been more effectively used in coordination with submarines for search, low-level attacks and mining in accelerating the destruction of Japanese shipping, or in destroying oil and metal plants in the southern areas, than in striking the Japanese "Inner Zone" from China bases.
In the final assault on the Japanese home islands we were handicapped by a lack of prewar economic intelligence. Greater economy of effort could have been attained, and much duplicative effort avoided, by extending and accelerating the strangulation of the Japanese economy already taking place as a result of prior attacks on shipping. This could have been done by an earlier commencement of the aerial mining program, concentration of carrier plane attacks in the last months of the war on Japan's remaining merchant shipping rather than on her already immobilized Warships, and a coordinated B-29 and carrier attack on Japan's vulnerable railroad system beginning in April 1945.
We underestimated the ability of our air attack on Japan's home islands, coupled as it was with blockade and previous military defeats, to achieve unconditional surrender without invasion. By July 1945, the weight of our air attack had as yet reached only a fraction of its planned proportion, Japan's industrial potential had been fatally reduced, her civilian population had lost its confidence in victory and was approaching the limit of its endurance, and her leaders, convinced of the inevitability of defeat, were preparing to accept surrender. The only remaining problem was the timing and terms of that surrender.
Having entered the war inadequately prepared, we continued all-out mobilization of all resources to bring ever increasing pressure on Japan, beyond the time when this was still reasonably required.
The problem of control of the air, primarily of our own air, and should we be attacked, of the enemy's air as well, becomes of even greater significance. The most intense effort must be devoted to perfecting defensive air control both by day and night, through the improvement of early warning and fighter control apparatus, anti-aircraft ordnance and defensive fighters, not only from the standpoint of technological improvement and volume, but also of disposition and tactics. It would be rash, however, to predict an increase in the effectiveness of defensive control sufficient to insure that not a single enemy plane or guided missile will be able to penetrate. It therefore behooves us to accept the possibility that at least a small
number of enemy planes or guided missiles may be able to evade all our defenses and to attack any objective within range.
The threat of immediate retaliation with a striking force of our own should deter any aggressor from attacking.
If we are not to be overwhelmed out of hand, in the event we are nevertheless attacked, we must reduce materially our vulnerability to such attack. The experience of both the Pacific and European wars emphasizes the extent to which civilian and other forms of passive defense can reduce a country's vulnerability to air attack. Civilian injuries and fatalities can be reduced, by presently known techniques, to one-twentieth or less of the casualties which would be suffered were these techniques not employed. This does not involve moving everything underground, but does involve a progressive evacuation, dispersal, warning, air-raid shelter, and postraid emergency assistance program, the foundations for which can only be laid in peacetime. The analysis of the effects of the atomic bombs at Hiroshima and Nagasaki indicates that the above statement is just as true and much more terrifyingly significant in an age of atomic bombs than it was in an age of conventional weapons. Similarly, economic vulnerability can be enormously decreased by a well worked out program of stockpiles, dispersal and special construction of particularly significant segments of industry. Such a program in the economic field can also be worked out satisfactorily only in peacetime.
In the strictly military field the impact of atomic weapons and guided missiles on strategy and tactics can only be developed by military specialists. It is the Survey's opinion, however, that mature study by such specialists will support the conclusion that dispersal of military forces, and therefore space and distance in which to effect such dispersal, will be significant considerations; that heavy bombers similar to those used in this war will not be able to operate effectively and on a sustained basis much beyond the range of protective fighters, and that newer types of offensive weapons and new tactics must be developed to do so; that forward air bases will have to be defended or more advanced bases acquired step by step in actual combat; and that the basic principles of war, when applied to include the field of the new weapons, will be found to remain. If such be the case, atomic weapons will not have eliminated the need for ground troops, for surface vessels, for air weapons, or for the full coordination among them, the supporting services and the civilian effort, but will have changed the context in which they are employed to such a degree that radically changed equipment, training and tactics will be required.
Research and development. -- The "blitzkrieg" technique is of enormous danger. This conclusion, derived initially from the European war, is strongly supported by the Japanese experience. A mobilized and well-trained striking force enjoying a certain technical superiority can overwhelm in short order the forces of a country of far greater basic long-term strength. In the opening phases of the Pacific war the Japanese were able to overrun 130,000,000 people and an area of enormous strategic importance in the space of a few months. This was true in spite of the fact that from the time of the Munich conference in 1938 we had been on notice that aggression against the peace of the world was possible and that the intervening years and the experience of our Allies had been invaluable in permitting us to take the necessary steps to revise our strategic concepts, to apply our advanced scientific and development resources to the improvement of our weapons, and to begin our industrial and military mobilization. The distances of the Pacific fortunately gave us space, and therefore time, in which to absorb the initial blow while our increasing strength and Japan's increasing logistic problems reversed the initial disadvantages facing our advanced forces.
Science has increased tremendously the destructive capability of modern weapons and promises further developments in the future. Given an adequate supply of atomic bombs, the B-29s based in the Marianas had sufficient strength to have effectively
destroyed in a single day every Japanese city with a population in excess of 30,000 people. In the future, national security will depend to a large degree on technical superiority of weapons and on operating and maintenance proficiency of personnel. Peacetime military strategic planning must be pointed to and supported by a vigorous program of scientific research and development.
If the United States is not to be forced to hasty and inadequate mobilization every time the threat of aggression arises in the world, it is essential that in the field of military weapons and tactics she be technically not merely abreast of, but actually ahead of any potential aggressor. It is not generally realized the degree to which basic scientific research was neglected in the United States during the course of the war in order to concentrate on the belated development of the specific weapons immediately required, nor the degree to which we lagged behind Germany in advanced aerodynamics, jet propulsion and the development of guided missiles. In air armament and torpedoes, even the Japanese were ahead of us. One or two years' lag in either basic research or in the development of reliable military application of such research can only be made up with difficulty, if at all. This type of work has become so complex that expenditures for research and development in the order of one billion dollars annually may be required to assure an acceptable degree of national security.
Intelligence. -- At the start of the Pacific war our strategic intelligence was highly inadequate, and our overall war plans, insofar as they were based on faulty information and faulty interpretation of accurate information, were unrealistic. After Pearl Harbor the obtaining and analysis of economic and industrial information necessary to the planning of an attack on Japan's sustaining resources required several years of the most strenuous effort and even then substantial gaps remained. If a comparable lack of intelligence should exist at the start of a future national emergency, it might prove disastrous.
In the field of operational intelligence considerable forward strides were made during the Pacific war. The requirements in this field for a large volume of minutely detailed and accurate work, for complex analysis geared to rapidly changing capabilities of forces and weapons, and for speed, all place a heavy burden on training, competence and organization. These requirements were not fully met in the Pacific war; the deficiency was at times serious. This was in large measure traceable to a prewar lack of trained and competent operational intelligence officers to provide an adequate nucleus for an expanding organization.
The basis for adequate intelligence can only be laid in peacetime. The solution to our problems in this held appears in part to be the greater centralization to be provided by the National Intelligence Authority, particularly in securing more adequate coordination and dissemination. It appears also to lie in close integration into the various operating organizations of appropriate intelligence units, adequate budgets and personnel for intelligence work, and a sufficient increase in the prestige attached to such work to attract the highest quality of personnel. This latter can only come from increased training in intelligence and active appreciation of its functions on the part of other Army, Navy, and Government officials. The present lack of recognized responsibility for intelligence work by the various operating organizations and the present shortage of trained and competent intelligence personnel give cause for alarm and require correction.
Integration of our military establishments. -- Organizational deficiencies in the Japanese Government contributed to Japan's entering a disastrous war and subsequently contributed to the absoluteness of her defeat. The form of her governmental organization provided no means for civilian control of the military or for obtaining effective coordination between the Army and Navy. Military policy was inconsistent with the foreign policy of the cabinet, the Japanese Army and Navy tending to make their own foreign policy in accordance with their individual aims, capabilities and requirements. During the war, bureaucratic rivalry between her Army and Navy impeded coordinated strategic and tactical planning, the proper employment of her air power, the development of adequate logistics and the efficient utilization of her economic resources. The existence of such joint or combined organizations as the Supreme War Council, the Supreme War Direction Council, the Board of Field Marshals and Fleet Admirals, the Imperial General Headquarters served mainly to hide the fact that real unity, integration, and coordination were conspicuously lacking.
Even though the United States did not achieve unity of command in the Pacific as a whole, each theater commander used the air, ground and sea forces assigned to him as an integrated or coordinated team. Coordination and compromise among theater commanders was largely achieved in all major respects. Such lack of complete integration as existed was in a large measure traceable back through the structure of the Joint Chiefs of Staff to the basic structure of our prewar military organization.
The Congress of the United States is today considering legislation for the reorganization and integration of our military establishments. The Survey is of the opinion that the prompt passage of appropriate legislation is in the national interest.
The lessons of the Pacific war strongly support that form of organization which provides unity of command, capable of clear and effective decision at the top, strengthens civilian control and thus provides closer integration of military policy with foreign and domestic policy, and favors a high degree of coordination in planning, intelligence, and research and development. Such unity of command should, however, decentralize administrative burdens and permit specialized training and the free development of the component forces, even at the risk of some duplication.
Within a department of common defense which provides unity of command and is itself oriented toward air and new weapons, the Survey believes that, in addition to the Army and the Navy, there should be an equal and coordinate position for a third establishment. To this establishment should be given primary responsibility for passive and active defense against long range attack on our cities, industries and other sustaining resources; for strategic attack, whether by airplane or guided missile; and for all air units other than carrier air and such land-based air units as can be more effective as component parts of the Army or Navy. The mission of such a new establishment would differ considerably from that of an autonomous air force and would, in certain respects, require additional and broader experience than has heretofore been required by the Army air forces alone.
Strength as a force for peace. -- The Survey's report on the European war stated that the great lesson to be learned in the battered cities of England and the ruined cities of Germany is that the best way to win a war is to prevent it from occurring. This is fully supported by the example of the devastated cities of Japan and their unhappy and hungry surviving inhabitants. The prevention of war must be the ultimate end to which our best efforts are devoted. It has been suggested, and wisely so, that this objective is well served by insuring the strength and the security of the United States. The United States was founded and has since lived upon principles of tolerance, freedom and good will at home and abroad. Strength based on these principles is no threat to world peace. Prevention of war will not be furthered by neglect of strength or lack of foresight or alertness on our part. Those who contemplate evil and aggression find encouragement in such neglect. Hitler relied heavily upon it. The Japanese would never have attacked Pearl Harbor had they not correctly assessed the weakness of our defenses in the Pacific and had they not incorrectly assessed the fighting determination of the United States when attacked.
Suggestions for assuring the military strength and security of the United States are by no means intended as a recommendation for a race in arms with other nations; nor do they reflect a lack of confidence in the prospect of international relationships founded upon mutual respect and good will which will themselves be a guarantee against future wars. The development of an intelligent and coordinated approach to American security can and should take place within the framework of the security organization of the United Nations.
The United States as a member of the United Nations has covenanted not to use force except in defense of law as embodied in the purposes and principles of the United Nations' Charter. As one of the great powers we must be prepared to act in defense of law and to do our share in assuring that other nations live up to their covenant.
The United States must have the will and the strength to be a force for peace.
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