Nuclear attacks against Japan

Nuclear weapons have never been used except twice by the United States against the Japanese at the very end of the Second World War in August, 1945. They were developed in a highly secret program during the war and were ready for use only after Germany, Japan's ally, had already surrendered.

The decision was controversial at the time, with the decisionmakers knowing less than we do today, both on the effects of nuclear weapons, and on the internal Japanese arguments about conditions under which they would surrender. It has been suggested that the U.S. Strategic Bombing Survey said the Japanese would have surrendered without the use of nuclear weapons, but the actual report emphasizes that opinion is made with the benefit of hindsight. The Report said:

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.

The Survey continued,

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.

Some "revisionists" have suggested Hiroshima was supposed to be an unmistakable signal to Stalin to play along diplomatically with the Americans who planned to rule the postwar world. Many have asked whether some sort of demonstration explosion should have been made, in order to frighten Tokyo without killing so many people. The option was considered, but with only two bombs available Truman decided instead to drop millions of leaflets upon Hiroshima and Nagasaki warning people to leave immediately, and at the Potsdam Conference he explicitly warned Japan it must surrender immediately or be hit with terrible force.

The civilian government in Tokyo wanted peace on conditional terms, but that was impossible because of Roosevelt's policy of unconditional surrender (Second World War), and because the civilians did not control Japan's decisions--the Army and Navy, under the Cabinet Law. Only the unprecedented direct intervention of the Emperor changed the balance of power.

Many factors led to the surrender of Japan. The nuclear bombings certainly were a part. The declaration of war by the Soviets, however, ended any hope for a negotiated peace. Even after Hiroshima and the invasion of Manchuria the Army and Navy wanted to fight on, while the civilians wanted to give up. With Roosevelt gone, the Americans redefined "unconditional" to allow continuance of the Emperor. Hirohito then broadcast an order to the nation and its armed forces to surrender, which was immediately obeyed.

Nuclear weapons development

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The decision to use nuclear weapons

There was no consensus, among the small number of senior military leaders aware of the bomb development, about the separable issues of military effectiveness of such attacks, and the ethics thereof. While the casualties that would actually be caused by nuclear attacks were not known, the fire-bombing of Tokyo probably caused a greater number of casualties.

The first bomb to be used, a uranium fission device of the "gun" type code-named LITTLE BOY, had not been tested; only theoretical calculations of effect were available. Physicists involved in its development were certain it would work, but less so about the plutonium implosion technology in the second bomb. In the TRINITY test in New Mexico, an implosion device of the type used on Nagasaki was tested, and better data was available.

From the TRINITY experience, however, it was clear that a nuclear explosion would be qualitatively different than any previous attack, and would have great psychological impact. Nevertheless, there were both military commanders, and scientists that worked on the bombs' development, that preferred such measures as an initial demonstration, for the Japanese, on an uninhabited target. Other commanders and scientists believed that the shock value of the weapons would contribute to the ending of the war. Further complicating the situation was that the new President, Harry Truman, had not been informed of the bomb development while Vice President, and had a short time to make the decision.

The U.S., in anticipation of a possible nuclear attack, had avoided heavy bombing of four cities, including Hiroshima and Nagasaki. This had two purposes: allowing better assessment of the weapon effects, and also having a greater shock value.

An argument against using these weapons was that Japan was clearly struggling under conventional bombings and the submarine blockade. Unfortunately, the U.S. had no sources inside the Japanese government, which would confirm that there was a stalemate between a hard-line faction that believed it appropriate to fight to the last Japanese, and a faction that was willing to examine a peace. The peace faction had come into being with the loss of Saipan and the resultant fall of the Tojo government, but the Allies had no hard information.

The primary argument was to use a radically different attack with the purpose of breaking the will of Japan, which actually was unlikely to affect the hard-liners. A secondary consideration was that the U.S. was planning a land invasion of Japan, with the first phase, Operation Olympic scheduled in October 1945, with the target of Kyūshū, which was under the command of Second General Army. That organization, comparable to an Allied army group, had its headquarters in Hiroshima Castle.

The U.S. Navy had very little to do with the atomic bomb decision. Having temporarily lost 5 of its 11 big carriers at Okinawa, it did not want to face the Kamikazes again during an invasion of Japan. It argued that the blockade was working well, cutting off nearly all oil, food and troop movements to and from Japan. It expected that the blockade would eventually lead to surrender. Civilians overruled them.

In July 1945 the Army Air Force saw its doctrine of strategic bombing working as intended. The original plan was to have used B-29 bombers, from high altitude, with greater precision than the B-17 and B-24 bombers used in Europe. Unexpected high-altitude winds proved this was impossible, and Gen. Curtis LeMay, newly commanding the strategic bombers, on his own authority changed to low-altitude incendiary bombing. He shed the machine guns and gunners, and the gasoline no longer needed to lift the planes to 30,000 feet. The result was a doubling of the bomb load, and very scared fliers who were greatly relieved to discover their losses were less using the new tactics. From the first raid on March 9, the new tactic was devastating. working to perfection. The B-29 dropping conventional high explosives and incendiaries was the perfect instrument to destroy the infrastructure of Japan's larger cities. The great bombing campaign had just started; it was planned to peak a year later. The atomic bomb was not part of AAF doctrine; the AAF generals had not been consulted, knew very little about the bomb and even demanded a direct order from President Truman before they agreed to explode it.

The Army agreed that the combination of blockade and strategic bombing would eventually destroy every Japanese city, but felt it could not destroy the Japanese Army, which was widely dispersed and dug in.

General Marshall worried that the American people might grow weary of more years of warfare, and might even demand some sort of compromise peace in order to bring the soldiers home. (Marshall underestimated the intense determination of nearly all Americans to destroy Japan.) Furthermore he objected to dropping the bombs on cities on moral and political grounds (Japan might become an enemy forever). Most of all, he had a tactical rather than strategic use in mind. Only a handful of bombs were being built, (two to four per month) and MacArthur's invasion forces ought to have all of them. Nine bombs had been allocated to "Operation Olympic". Marshall and his planners concluded that Japan would surrender only after ground troops captured Tokyo. The invasion of Kyushu was scheduled November 1; all bombs available then (probably seven) should be used there. They would give invading infantry forces enough firepower to destroy defensive ground installations, communications facilities, kill exposed enemy soldiers, and also block the arrival of reinforcements. To waste the precious bombs on irrelevant civilians would cause more American casualties, and like all the high American officials Marshall was committed to minimizing American--not Japanese-- losses.

Manhattan Project

President Harry S. Truman, who had been completely frozen out of decision making and secret information before he suddenly became President in April, did not know what he wanted to do. He lurched this way then that, depending on who talked to him last. The man who talked to him last about the bomb was Henry Stimson. Stimson rarely participated in strategic planning, but he had one card up his sleeve--the atomic bomb. To build it, Roosevelt, set up the Manhattan Project.

The Manhattan Project was managed by Major General Leslie Groves (Corps of Engineers) with a staff of reservists and many thousands of civilian scientists and engineers. Nominally Groves reported directly to Marshall, but in fact Stimson was in charge. Stimson secured the necessary money and approval from Roosevelt and from Congress, and made sure Manhattan had the highest priorities. He controlled all planning for the use of the bomb, overruling the high command of the Army, Navy and AAF in the process. He wanted "Little Boy" (the Hiroshima bomb) dropped within hours of its earliest possible availability. And it was. Stimson wanted Japan to surrender, and thought the Hiroshima bomb on August 6 would provide the final push Tokyo needed. When nothing seemed to happen he had Truman drop "Fat Man" on Nagasaki on August 9. The Japanese offered to surrender on August 10.

Impact on Japan

The Strategic Bombing Survey did confirm that the weapons had a major psychological effect on the populace:

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).

Popular opinion was simply not of concern to the deadlocked Imperial Cabinet. Only the unprecedented intervention by the Emperor broke the tie in the direction of the peace faction. The U.S. accepted less than the unconditional surrender it had been demanding, not having known that the chief argument of the hard-liners was the continuation of the monarchy, the one condition on which the Japanese insisted.

Ethics debate on Strategic Bombing

During the war prewar pacifists and a few churchmen (especially Catholics troubled over the bombing of Catholic cities like Rome and Cologne) began to question the morality of bombing cities. After Hiroshima the issue focused on the atomic bomb, with much of the discussion echoing the fears of the interwar period about flotillas of enemy bombers dropping poison gas on New York City.

This time the technology was capable of mass destruction; everyone had genuine fears of a nuclear war that would kill tens of millions of Americans within minutes. Only the United States had ever used atomic weapons--and in both cases the victims were civilian populations. Many of the top soldiers thought the atomic bomb was unnecessary--that their particular strategy would have won the war eventually.

Each of the alternative strategies, however (such as the Army invasion of Kyushu and Honshu, the Navy's tight blockade, the Air Force's relentless firebombing) would have produced more American casualties--and probably far more Japanese killed. Some historians, starting form the assumption that the bomb was "unnecessary" have speculated that it must therefore have been used for some motivation other than military victory.

Perhaps the bureaucratic dynamics of the Manhattan Project were such that the bomb had to be dropped to prove the expenditures on it were not wasted? This was highly unlikely, since Truman would not have been blamed for expenditures that took place before he took charge. Other historians suggest that the bomb was dropped in order to influence or frighten the Russians, or perhaps to keep them out of the war. In fact the Pentagon, the State Department and the White House had been begging the Russians to enter the war, and at no time did Truman ever suggest to Stalin that in fact his entry into the Pacific war was unnecessary or unwanted.

As for frightening the Russians, that seems unlikely too. Truman and Stimson knew that Russia had the capability of building their own bomb; unleashing the American weapon was less likely to frighten the dedicated Communists than to divert them from peaceful recovery into a new arms race.