Economic Effects of Air Attack Against the Japanese Home Islands

The physical destruction resulting from the air attack on Japan approximates that suffered by Germany, even though the tonnage of bombs dropped was far smaller. The attack was more concentrated in time, and the target areas were smaller and more vulnerable. Not only were the Japanese defenses overwhelmed, but Japan's will and capacity for reconstruction, dispersal, and passive defense were less than Germany's. In the aggregate some 40 percent of the built-up area of the 66 cities attacked was destroyed. Approximately 30 percent of the entire urban population of Japan lost their homes and many of their possessions. The physical destruction of industrial plants subjected to high-explosive attacks was similarly impressive. The larger bomb loads of the B-29s permitted higher densities of bombs per acre in the plant area, and on the average somewhat heavier bombs were used. The destruction was generally more complete than in Germany. Plants specifically attacked with high explosive bombs were, however, limited in number.

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.