Strategic Bombing

National Archives. Via Frank (1999)

Strategic bombing was one of the most controversial aspects of the Second World War, from both a military and moral perspective. The possibility that a nation could be defeated solely by air attacks on its economic infrastructure was studied extensively by air power advocates in the interwar period, and, by 1939, many national air forces had become dominated by a "bomber cult." However, many civilian leaders had serious moral qualms about the collateral damage to noncombatants that would be inevitable in a strategic bombing campaign.

The Hague Conventions banned bombs and projectiles dropped from balloons, but were never updated to include attacks from heavier-than-air aircraft. Indiscriminate attacks on civilians were generally considered a violation of the customs of war, but the legal status of attacks on cities containing military facilities or war industries was unclear. Japan engaged in indiscriminate bombing in China (particularly of Chungking), and Germany carried out bombings of Warsaw in Poland and Rotterdam in the Netherlands that were highly questionable from a military or economic warfare perspective.

Initially, the Allies avoided strategic bombing. There is a famous anecdote that Chamberlain, Churchill's predecessor as Prime Minister of the United Kingdom, refused to give his air commanders permission to bomb the German arms factories in the Ruhr on the grounds that they were private property. Long-range bombing was limited to obvious military targets, such as the naval base at Wilhemshaven. This changed during the Battle of Britain. A German bomber flight became lost and jettisoned its bombs, as it turned out, over the East End of London. Britain retaliated with a bombing raid against Berlin that came nowhere near the city center (night aerial navigation being very primitive) but infuriated the Nazi leadership. This led to the "Blitz" against British cities, in which tens of thousands of civilians were killed and many more left homeless. At this point, moral qualms were largely abandoned in favor of an "if that's how they want to play the game ..." attitude. The Allied leadership seemed to feel that the Axis, having sown the wind, were entitled to reap the whirlwind.

The military effectiveness of strategic bombing in Europe is as controversial as its morality. German production actually increased during the peak of the strategic bombing campaign, though most of the increased production was in occupied countries out of range of Allied bombers. The morale of the German people never cracked under bombardment, contrary to the expectations of Allied air commanders. Bomber casualties were heavy. This was particularly true among American bomber crews, since the Americans grossly overestimated the survivability of their strategic bombers on daylight raids. Ironically, the decision to risk heavy casualties in daylight bombing was based on a belief in precision bombing, which specifically targeted factories and communications rather than civilians. British bombers were employed for area bombing at night, but also began to suffer serious casualties as German night fighter defenses improved.

However, once long-range fighters began escorting American bombers, casualties soared among the defending German fighter pilots. This was a major contributing factor to the collapse of the Luftwaffe in the West and the success of the Anglo-American invasion of France. When the Allies finally focused their strategic bombing on synthetic fuel plants and other petroleum facilities, early in 1945, the Germans quickly ran out of fuel. This was an important contributing factor to the collapse of the Wehrmacht. However, the Russian capture of the oilfields in Romania and Austria were probably as important as the strategic bombing campaign.

Strategic Bombing in the Pacific

Although the Japanese indulged in terror bombing in China, they never developed a true strategic bomber. Navy bombers such as the G3M "Nell", with its very long range, proved vulnerable to fighter defenses but bombed with impunity wherever they could be escorted by the A5M "Claude" or the A6M "Zero". Heavy bombing attacks on Chungking, Kunming, and other cities wrecked any possibility the Chinese had of building up a sizable arms production industry. When war broke out in the Pacific and the American Volunteer Group began operating in China, Japanese strategic bombing came virtually to a halt.

The Americans began the war with the B-17 Flying Fortress, arguably the world's first true strategic bomber. Both the B-17 and its successor, the B-24 Liberator, were used extensively for patrolling and tactical bombing in the Pacific. Neither had the range to reach important strategic targets deep in the Japanese Empire.

This picture began to change on 15 June 1944, when the first B-29 Superfortress raid reached Kyushu from 20 Air Force bases in China. At first, the Superfortresses carried out daylight precision bombing raids, but these were disappointing. High-altitude flying conditions over Japan were miserable due to the proximity of the jet stream. In addition, Japan is frequently cloud-covered, and the Allies started with meager intelligence on most targets.

With the capture of the larger Mariana Islands, the U.S. strategic air forces were able to establish airfields that had an adequate line of supply and from which the B-29s could reach most of Japan. The results of high-altitude daylight precision bombing continued to disappoint, however. When General LeMay took over 21 Air Force, he switched to night area bombing using incendiaries. By bombing at night, the B-29s could fly at lower altitude and with less defensive armament, allowing more incendiaries to be carried to the targets. The incendiaries themselves were more potent than ever, containing a combination of napalm and magnesium.

The first raid using the new tactics, against Tokyo on the night of 9-10 March 1945, involved 279 B-29s dropping over 1650 tons of incendiaries. A firestorm was successfully raised, and the death toll was somewhere between 80,000 and 120,000 persons. This was probably the most devastating single air raid of the war, exceeding even the nuclear raids. From then on, the U.S. strategic air forces began systematically burning the cities of Japan to the ground.

Japanese defenses were pitifully inadequate and civil defense was rudimentary. Tokyo had just 18 concrete air raid shelters with a combined capacity of 5,000 persons. The coastal plains on which most of Japan's cities were built were composed of unstable soil derived from volcanic ash, which hindered excavation. The only shelter for most civilians was bokugo, small holes six to 15 feet (two to five meters) long, three feet (one meter) across, and four to six feet (1.5 to 2 meters) deep, with bamboo roofs covered with a thin layer of dirt. These were dug next to homes or along streets, and proved almost useless. Tokyo authorities had ordered the demolition of some 207,370 homes to produce 31 miles of firebreaks by March 1944, but in many cases the timber from the demolished homes had not yet been removed.

LeMay justified this campaign of mass destruction with the observation that Japanese industry, while concentrated in the largest cities, was fairly dispersed within those cities. Most Japanese factories relied on parts manufactured on what was nearly a cottage basis in small neighborhood workshops. LeMay later stated that

We were going after military targets. No point in slaughtering civilians for the mere sake of slaughter. Of course there is a pretty thin veneer in Japan, but the veneer was there. It was their system of dispersal of industry.... I'll never forget Yokohama. That was what impressed me: drill presses. There they were, like a forest of scorched trees and stumps, growing up throughout the residential area. Flimsy construction all gone ... everything burned down, or up, and drill presses standing like skeletons.

Dr. Karl T. Compton made a similar observation to Truman in October 1945 (Frank 1999):

Standing in the ashes of a substantial portion of the burned homes [in Tokyo] are various types of machine tools like lathes, drill presses, etc. Here family groups were manufacturing repetitive parts like nuts, bolts, or coils which were delivered to the manufacturing centers for use in the assembly of military weapons. In the area we examined, approximately one fifth of the homes showed evidence of such activities.

Another factor underlying LeMay's departure from the previous American insistence on precision daylight bombing was the mass suicides of civilians on Saipian, which suggested to some that there was no meaningful distinction between Japanese combatants and noncombatants.

Later in the campaign, leaflets would be dropped a day or two in advance of a raid, announcing the next target and admonishing civilians to flee to the countryside. It is unlikely this was motivated primarily by humanitarians concerns. It was more likely a form of psychological warfare, demonstrating to Japanese civilians that their government was powerless to protect them even when raids were announced well in advance. There is some evidence that this form of psychological warfare was highly effective.

Total casualties and damage from the strategic bombing campaign are give in the table below (Frank 1999).

A different form of strategic bombing was aerial offensive mine laying. These missions were inexpensive and very effective at shutting down Japanese coastal shipping. Aerial mine laying by Superfortresses began with Operation Starvation, which laid 900 mines in April 1945. Shimonoseki Strait was shut down for two weeks and total Japanese imports dropped by half. Desperate Japanese commanders ordered ships to run the strait anyway, resulting in heavy shipping losses. By the end of the war, the Superfortresses had laid 12,000 mines and were responsible for 63% of all shipping losses suffered by the Japanese during the period of the mining campaign. The mine campaign is summarized in the table below (Frank 1999).

Also of strategic importance was the sinking by carrier aircraft on 14-15 July 1945 of eight of the twelve railway ferries that carried traffic between Hokkaido and Honshu. This immediately halved deliveries of coal to Honshu.

The ultimate expression of strategic bombing were the nuclear attacks on Hiroshima and Nagasaki. The importance of these raids in forcing the Japanese to surrender has been questioned, but they were likely a major factor (along with the sea blockade and the Russian invasion of Manchuria) in the Emperor's final decision.

The overall effects of the strategic bombing campaign are disputed. Industrial productivity in most categories was reduced to about half its 1944 peak by July 1945. Aluminum production had come to a near standstill at 9% of its 1944 peak. However, the massive drop in productivity likely owes at least as much to the destruction of the Japanese merchant marine, and the resulting loss of imports of raw materials, as to the destruction of the factories themselves.

Had the war continued past August 1945, the next target for strategic bombing was to be Japan's rail system. Because of Japan's mountainous terrain, the rail system was unusually vulnerable to attack, which would have made it impossible to move vital commodities such as rice. Frank (1999) has argued that this would have led to widespread famine that would have forced a surrender without the nuclear attacks, but at the cost of perhaps as many as ten million deaths by starvation. As it was, disastrous declines in rice production coupled with blockade meant that the occupation authorities had to import 800,000 tons of food in 1946.

References

Drea (2009)

Frank (1999)
Hastings (2007)

The Pacific War Online Encyclopedia © 2007-2009 by Kent G. Budge. Index

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