Prelude to the bombings : The Manhattan Project
The United States, with assistance from the United Kingdom and Canada, designed and built the first atomic bombs under what was called the Manhattan Project. The project was initially started at the instigation of European refugee scientists (including Albert Einstein) and American scientists who feared that Nazi Germany would also be conducting a full-scale bomb development program (this was later discovered to be incorrect). The project itself eventually employed over 130,000 people at its peak at over thirty institutions spread over the United States, and cost a total of nearly $2 billion USD, making it one of the most enormous research and development programs of all time.
The first nuclear device, called "Gadget," was detonated during the "Trinity" test near Alamogordo, New Mexico on July 16, 1945. The Hiroshima and Nagasaki bombs were the second and third to be detonated and the only ones ever employed as weapons.
During World War II both the Allies and Axis powers had previously pursued policies of strategic bombing and the targeting of civilian infrastructure. In numerous cases these had caused huge numbers of civilian casualties and were (or came to be) controversial. In Germany, the Allied firebombing of Dresden resulted in roughly 30,000 deaths. The March 1945 firebombing of Tokyo may have killed as many as 100,000 people. By August, about 60 Japanese cities had been destroyed through a massive aerial campaign, including massive firebombing raids on the cities of Tokyo and Kobe.
Over 3½ years of direct U.S. involvement in World War II, approximately 400,000 American lives had been lost, roughly half of them incurred in the war against Japan. In the months prior to the bombings, the Battle of Okinawa resulted in an estimated 50–150,000 civilian deaths, 100–125,000 Japanese or Okinawan military or conscript deaths and over 72,000 American casualties. An invasion of Japan was expected to result in casualties many times greater than in Okinawa.
U.S. President Harry S. Truman, who was unaware of the Manhattan Project until Franklin Roosevelt's death, made the decision to drop the atomic bombs on Japan. His stated intention in ordering the bombings was to bring about a quick resolution of the war by inflicting destruction, and instilling fear of further destruction, that was sufficient to cause Japan to surrender. On July 26, Truman and other allied leaders issued The Potsdam Declaration outlining terms of surrender for Japan:
"...The might that now converges on Japan is immeasurably greater than that which, when applied to the resisting Nazis, necessarily laid waste to the lands, the industry and the method of life of the whole German people. The full application of our military power, backed by our resolve, will mean the inevitable and complete destruction of the Japanese armed forces and just as inevitably the utter devastation of the Japanese homeland..."
"...We call upon the government of Japan to proclaim now the unconditional surrender of all Japanese armed forces, and to provide proper and adequate assurances of their good faith in such action. The alternative for Japan is prompt and utter destruction."
The next day, Japanese papers reported that the declaration, the text of which had been broadcast and dropped on leaflets into Japan, had been rejected. The atomic bomb was still a highly guarded secret and not mentioned in the declaration.
Choice of targets
The Target Committee at Los Alamos on May 10–11, 1945, recommended Kyoto, Hiroshima, Yokohama, and the arsenal at Kokura as possible targets. The committee rejected the use of the weapon against a strictly military objective because of the chance of missing a small target not surrounded by a larger urban area. The psychological effects on Japan were of great importance to the committee members. They also agreed that the initial use of the weapon should be sufficiently spectacular for its importance to be internationally recognized. The committee felt Kyoto, as an intellectual center of Japan, had a population "better able to appreciate the significance of the weapon." Hiroshima was chosen because of its large size, its being "an important army depot" (a description which nowadays seems to have been exaggerated) and the potential that the bomb would cause greater destruction because the city was surrounded by hills which would have a "focusing effect".
Secretary of War Henry L. Stimson struck Kyoto from the list because of its cultural significance, over the objections of General Leslie Groves, head of the Manhattan Project. According to Professor Edwin O. Reischauer, Stimson "had known and admired Kyoto ever since his honeymoon there several decades earlier." On July 25 General Carl Spaatz was ordered to bomb one of the targets: Hiroshima, Kokura, Niigata, or Nagasaki as soon after August 3 as weather permitted and the remaining cities as additional weapons became available.
Hiroshima during World War II
At the time of its bombing, Hiroshima was a city of considerable industrial and military significance. Even some military camps were located nearby, such as the headquarters of the Fifth Division and Field Marshal Shunroku Hata's 2nd General Army Headquarters, which commanded the defense of all of southern Japan. Hiroshima was a minor supply and logistics base for the Japanese military. The city was a communications center, a storage point, and an assembly area for troops. It was one of several Japanese cities left deliberately untouched by American bombing, allowing an ideal environment to measure the damage caused by the atomic bomb. Another account stresses that after General Spaatz reported that Hiroshima was the only targeted city without prisoner of war (POW) camps, Washington decided to assign it highest priority.
The center of the city contained several reinforced concrete buildings and lighter structures. Outside the center, the area was congested by a dense collection of small wooden workshops set among Japanese houses. A few larger industrial plants lay near the outskirts of the city. The houses were of wooden construction with tile roofs, and many of the industrial buildings also were of wood frame construction. The city as a whole was highly susceptible to fire damage.
The population of Hiroshima had reached a peak of over 381,000 earlier in the war, but prior to the atomic bombing the population had steadily decreased because of a systematic evacuation ordered by the Japanese government. At the time of the attack the population was approximately 255,000. This figure is based on the registered population used by the Japanese in computing ration quantities, and the estimates of additional workers and troops who were brought into the city may be inaccurate.
Hiroshima was the primary target of the first U.S. nuclear attack mission, on August 6, 1945. The B-29 Enola Gay, piloted and commanded by Colonel Paul Tibbets, was launched from Tinian airbase in the West Pacific, approximately 6 hours flight time away from Japan. The drop date of August 6 was chosen because there had previously been a cloud formation over the target. At the time of launch, the weather was good, and the crew and equipment functioned properly. Navy Captain William Parsons armed the bomb during the flight, since it had been left unarmed to minimize the risks during takeoff. In every detail, the attack was carried out exactly as planned, and the gravity bomb, a gun-type fission weapon, with 60 kg (130 pounds) of uranium-235, performed precisely as expected.
About an hour before the bombing, the Japanese early warning radar net detected the approach of some American aircraft headed for the southern part of Japan. The alert had been given and radio broadcasting stopped in many cities, among them Hiroshima. The planes approached the coast at a very high altitude. At nearly 08:00, the radar operator in Hiroshima determined that the number of planes coming in was very small—probably not more than three—and the air raid alert was lifted (to conserve fuel and aircraft, the Japanese had decided not to intercept small formations).
The three planes present were the Enola Gay (named after Colonel Tibbets' mother), The Great Artiste (a recording and surveying craft), and a then-nameless plane later called Necessary Evil (the photographing plane). The normal radio broadcast warning was given to the people that it might be advisable to go to air-raid shelters if B-29s were actually sighted, but no raid was expected beyond some sort of reconnaissance. At 08:15, the Enola Gay dropped the nuclear bomb called "Little Boy" over the center of Hiroshima. It exploded about 600 meters (2,000 feet) above the city with a blast equivalent to 13 kilotons of TNT, instantly killing an estimated 70,000–80,000 people. Of this number, there were approximately 2,000 Japanese Americans who died from the blast and another 800-1,000 who lived on as hibakusha. As U.S. citizens, many of these Japanese Americans were attending school before the war and had been unable to leave Japan. At least 11 U.S. POWs also died. The radius of total destruction was about 1.6 km (1 mile), with resulting fires across 11.4 square km (4.4 square miles). Infrastructure damage was estimated at 90% of Hiroshima's buildings being either damaged or completely destroyed.
The Tokyo control operator of the Japanese Broadcasting Corporation noticed that the Hiroshima station had gone off the air. He tried to re-establish his program by using another telephone line, but it too had failed. About twenty minutes later the Tokyo railroad telegraph center realized that the main line telegraph had stopped working just north of Hiroshima. From some small railway stops within 16 kilometers (10 mi) of the city came unofficial and confused reports of a terrible explosion in Hiroshima. All these reports were transmitted to the headquarters of the Japanese General Staff.
Military bases repeatedly tried to call the Army Control Station in Hiroshima. The complete silence from that city puzzled the men at headquarters; they knew that no large enemy raid had occurred and that no sizeable store of explosives was in Hiroshima at that time. A young officer of the Japanese General Staff was instructed to fly immediately to Hiroshima, to land, survey the damage, and return to Tokyo with reliable information for the staff. It was generally felt at headquarters that nothing serious had taken place and that it was all a rumor.
The staff officer went to the airport and took off for the southwest. After flying for about three hours, while still nearly 100 miles (160 km) from Hiroshima, he and his pilot saw a great cloud of smoke from the bomb. In the bright afternoon, the remains of Hiroshima were burning. Their plane soon reached the city, around which they circled in disbelief. A great scar on the land still burning and covered by a heavy cloud of smoke was all that was left. They landed south of the city, and the staff officer, after reporting to Tokyo, immediately began to organize relief measures.
Tokyo's first knowledge of what had really caused the disaster came from the White House public announcement in Washington, D.C., sixteen hours after the nuclear attack on Hiroshima.
Radiation poisoning and necrosis caused illness and death after the bombing in about 1% of Hiroshima residents who survived the initial explosion. By December of 1945, thousands had died from their injuries and radiation poisoning, bringing the total killed in Hiroshima in 1945 to perhaps 140,000. In the years between 1950 and 1990, it is statistically estimated that hundreds of deaths are attributable to radiation exposure among atomic bomb survivors from both Hiroshima and Nagasaki.
Some of the reinforced concrete buildings in Hiroshima were very strongly constructed because of the earthquake danger in Japan, and their framework did not collapse even though they were fairly close to the center of damage in the city. Since the bomb detonated in the air, the blast was more downward than sideways, which was largely responsible for the survival of the Prefectural Industrial Promotional Hall, now commonly known as the Genbaku, or A-bomb Dome designed and built by the Czech architect Jan Letzel, which was only a few meters from ground zero. The ruin was named Hiroshima Peace Memorial and made a UNESCO World Heritage site in 1996 over the objections of the U.S. and China.
Events of August 7-9
After the Hiroshima bombing, President Truman announced, "If they do not now accept our terms, they may expect a rain of ruin from the air the likes of which has never been seen on this earth." On August 8, 1945, leaflets were dropped and warnings were given to Japan by Radio Saipan. (The area of Nagasaki did not receive warning leaflets until August 10, though the leaflet campaign covering the whole country was over a month into its operations.) An English translation of that leaflet is available at PBS.
At one minute past midnight on August 9, Tokyo time, Russian infantry, armor, and air forces launched an invasion of Manchuria. Four hours later, word reached Tokyo that the Soviet Union had broken the neutrality pact and declared war on Japan. The senior leadership of the Japanese Army took the news in stride, grossly underestimating the scale of the attack. They did start preparations to impose martial law on the nation, with the support of Minister of War Anami, in order to stop anyone attempting to make peace.
Responsibility for the timing of the second bombing was delegated to Colonel Tibbets as commander of the 509th Composite Group on Tinian. Scheduled for August 11 against Kokura, the raid was moved forward to avoid a five day period of bad weather forecast to begin on August 10.
The city of Nagasaki had been one of the largest sea ports in southern Japan and was of great wartime importance because of its wide-ranging industrial activity, including the production of ordnance, ships, military equipment, and other war materials.
In contrast to many modern aspects of Hiroshima, the bulk of the residences were of old-fashioned Japanese construction, consisting of wood or wood-frame buildings, with wood walls (with or without plaster), and tile roofs. Many of the smaller industries and business establishments were also housed in buildings of wood or other materials not designed to withstand explosions. Nagasaki had been permitted to grow for many years without conforming to any definite city zoning plan; residences were erected adjacent to factory buildings and to each other almost as closely as possible throughout the entire industrial valley.
Nagasaki had never been subjected to large-scale bombing prior to the explosion of a nuclear weapon there. On August 1, 1945, however, a number of conventional high-explosive bombs were dropped on the city. A few hit in the shipyards and dock areas in the southwest portion of the city, several hit the Mitsubishi Steel and Arms Works and six bombs landed at the Nagasaki Medical School and Hospital, with three direct hits on buildings there. While the damage from these bombs was relatively small, it created considerable concern in Nagasaki and many people—principally school children—were evacuated to rural areas for safety, thus reducing the population in the city at the time of the nuclear attack.
To the north of Nagasaki there was a camp holding British prisoners of war. They were working in the coal mines and only found out about the bombing when they came to the surface. For them, it was the bomb that saved their lives. However at least eight known POWs died.
On the morning of August 9, 1945, the U.S. B-29 Superfortress Bockscar, flown by the crew of 393rd Squadron commander Major Charles W. Sweeney, carried the nuclear bomb code-named "Fat Man." The mission plan for the second attack was nearly identical to that of the Hiroshima mission, with Kokura as the primary target and Nagasaki the secondary target. Two additional B-29's were to fly in instrumentation and photographic support of the mission.
Weather scouts aboard the Enola Gay flying in advance of the mission reported both targets clear. When Sweeny's aircraft arrived at the assembly point for the three planes off the coast of Japan, the third plane (V91, later called Necessary Evil and flown by Lt.Col. James I. Hopkins), failed to make the rendezvous. Bockscar and The Great Artiste circled for forty minutes without locating the third plane. By that time clouds had completely obscured Kokura. After three runs over the city and having fuel running low because of a fuel-transfer problem, they headed for their secondary target, Nagasaki. At about 07:50 Japanese time, an air raid alert was sounded in Nagasaki, but the "all clear" signal was given at 08:30. When only two B-29 Superfortresses were sighted at 10:53, the Japanese apparently assumed that the planes were only on reconnaissance and no further alarm was given.
A few minutes later, at 11:00, the observation B-29 flown by Captain Frederick C. Bock dropped instruments attached to three parachutes. These instruments also contained messages to Professor Ryokichi Sagane, a nuclear physicist at the University of Tokyo who studied with three of the scientists responsible for the atomic bomb at the University of California, Berkeley, urging him to tell the public about the danger involved with these weapons of mass destruction. The messages were found by military authorities but not turned over to Sagane.
At 11:02, a last minute break in the clouds over Nagasaki allowed Bock's Car's bombardier, Captain Kermit Beahan, to visually sight the target as ordered. The "Fat Man" weapon, containing a core of ~6.4 kg (14.1 lb) of plutonium-239, was dropped over the city's industrial valley. It exploded 469 meters (1,540 feet) above the ground exactly halfway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works (Torpedo Works) in the north. This was nearly 3 kilometers (2 mi) northwest of the planned hypocenter; the blast was confined to the Urakami Valley and a major portion of the city was protected by the intervening hills.
According to most estimates, about 70,000 of Nagasaki's 240,000 residents were killed instantly, and up to 60,000 were injured. The radius of total destruction was about 1.6 km (1 mile), followed by fires across the northern portion of the city to 3.2 km (2 miles) south of the bomb. The total number of residents killed is believed to be as many as 80,000, including those who died from radiation poisoning in the following months.
The survivors of the bombings are called hibakusha (被爆者), a Japanese word that literally translates to "people exposed to the bomb". The suffering of the bombing is the root of Japan's postwar pacifism, and the nation has sought the abolition of nuclear weapons from the world ever since. As of 2005, there are about 266,000 hibakusha still living in Japan.
During the war Japan brought many Korean conscripts to both Hiroshima and Nagasaki to work as forced labor. According to recent estimates, about 20,000 Koreans were killed in Hiroshima and about 2,000 died in Nagasaki. It is estimated that one in seven of the Hiroshima victims was of Korean ancestry For many years Koreans had a difficult time fighting for recognition as atomic bomb victims and were denied health benefits. Though such issues have been somewhat addressed in recent years, such issues and resentments regarding recognition continue to linger.
During the year after the bombing, approximately 40,000 U.S. occupation troops were in Hiroshima. Nagasaki was occupied by 27,000 troops. Upper limit dose estimates for those troops are 0.03 rem for Hiroshima, 0.08 rem for Nagasaki, and 0.63 rem for the Nishiyama area.
Although supporters of the bombing concede that the civilian leadership in Japan was cautiously and discreetly sending out diplomatic communiques as far back as January 1945, following the Allied invasion of Luzon in the Philippines, they point out that Japanese military officials were unanimously opposed to any negotiations before the use of the atomic bomb.
While some members of the civilian leadership did use covert diplomatic channels to begin negotiation for peace, on their own they could not negotiate surrender or even a cease-fire. Japan, as a Constitutional Monarchy, could only enter into a peace agreement with the unanimous support of the Japanese cabinet, and this cabinet was dominated by militarists from the Japanese Imperial Army and the Japanese Imperial Navy, all of whom were initially opposed to any peace deal. A political stalemate developed between the military and civilian leaders of Japan with the military increasingly determined to fight despite the costs and odds. Many continued to believe that Japan could negotiate more favorable terms of surrender by continuing to inflict high levels of casualties on opposing forces and end the war without an occupation of Japan or a change of government.
Historian Victor Davis Hanson points to the increased Japanese resistance, futile though it was in retrospect, as it became obvious that the result of the war could not be overturned by the Axis powers. The Battle of Okinawa showed this determination to fight on at all costs. More than 120,000 Japanese and 18,000 American troops were killed in the bloodiest battle of the Pacific theater, just 8 weeks before Japan's final surrender. In fact, more civilians died in the Battle of Okinawa than did in the initial blast of the atomic bombings. When the Soviet Union declared war on Japan on August 8, 1945, and carried out Operation August Storm, the Japanese Imperial Army ordered its ill-supplied and weakened forces in Manchuria to fight to the last man. Major General Masakazu Amanu, chief of the operations section at Japanese Imperial Headquarters, stated that he was absolutely convinced his defensive preparations, begun in early 1944, could repel any Allied invasion of the home islands with minimal losses.
After the realization that the destruction of Hiroshima was from a nuclear weapon, the civilian leadership gained more traction in its argument that Japan had to concede defeat and accept the terms of the Potsdam Declaration. Even after the destruction of Nagasaki, the emperor himself needed to intervene to end a deadlock in the cabinet.
According to some Japanese historians, Japanese civilian leaders who favored surrender saw their salvation in the atomic bombing. The Japanese military was steadfastly refusing to give up, as were the military men in the war cabinet. (Because the cabinet functioned by consensus, even one holdout could prevent it from accepting the declaration.) Thus the peace faction seized on the bombing as a new argument to force surrender. Koichi Kido, one of Emperor Hirohito's closest advisors, stated: "We of the peace party were assisted by the atomic bomb in our endeavor to end the war." Hisatsune Sakomizu, the chief Cabinet secretary in 1945, called the bombing "a golden opportunity given by heaven for Japan to end the war." According to these historians and others, the pro-peace civilian leadership was able to use the destruction of Hiroshima and Nagasaki to convince the military that no amount of courage, skill and fearless combat could help Japan against the power of atomic weapons. Akio Morita, founder of Sony and a Japanese Naval officer during the war, also concludes that it was the atomic bomb and not conventional bombings from B-29s that convinced the Japanese military to agree to peace.
Supporters of the bombing also point out that waiting for the Japanese to surrender was not a cost-free option—as a result of the war, noncombatants were dying throughout Asia at a rate of about 200,000 per month. Firebombing had killed well over 100,000 people in Japan since February of 1945, directly and indirectly. That intensive conventional bombing would have continued prior to an invasion. The submarine blockade and the United States Army Air Forces's mining operation, Operation Starvation, had effectively cut off Japan's imports. A complementary operation against Japan's railways was about to begin, isolating the cities of southern Honshu from the food grown elsewhere in the Home Islands. This, combined with the delay in relief supplies from the Allies, could have resulted in a far greater death toll in Japan from famine and malnutrition than actually occurred in the attacks. "Immediately after the defeat, some estimated that 10 million people were likely to starve to death," noted historian Daikichi Irokawa. Meanwhile, in addition to the Soviet attacks, offensives were scheduled for September in southern China and Malaysia.
The Americans anticipated losing many soldiers in the planned invasion of Japan, although the actual number of expected fatalities and wounded is subject to some debate and depends on the persistence and reliability of Japanese resistance and whether the Americans would have invaded only Kyushu in November 1945 or if a follow up landing near Tokyo, projected for March of 1946, would have been needed. Years after the war, Secretary of State James Byrnes claimed that 500,000 American lives would have been lost—and that number has since been repeated authoritatively, but in the summer of 1945, U.S. military planners projected 20,000–110,000 combat deaths from the initial November 1945 invasion, with about three to four times that number wounded. (Total U.S. combat deaths on all fronts in World War II in nearly four years of war were 292,000.) However, these estimates were done using intelligence that grossly underestimated Japanese strength being gathered for the battle of Kyushu in numbers of soldiers and kamikazes, by factors of at least three. Many military advisors held that a worst-case scenario could involve up to 1,000,000 American casualties.
The atomic bomb hastened the end of the Second World War in Asia liberating hundreds of thousands of Western citizens, including about 200,000 Dutch and 400,000 Indonesians ("Romushas") from Japanese concentration camps. Moreover, Japanese troops had committed atrocities against millions of civilians (such as the infamous Nanking Massacre), and the early end to the war prevented further bloodshed.
Supporters also point to an order given by the Japanese War Ministry on August 1, 1944. The order dealt with the disposal and execution of all Allied POWs, numbering over 100,000, if an invasion of the Japanese mainland took place. It is also likely that, considering Japan's previous treatment of POWs, were the Allies to wait out Japan and starve it, the Japanese would have killed all Allied POWs and Chinese prisoners.
In response to the argument that the large-scale killing of civilians was immoral and a war crime, supporters of the bombings have argued that the Japanese government waged total war, ordering many civilians (including women and children) to work in factories and military offices and to fight against any invading force. Father John A. Siemes, professor of modern philosophy at Tokyo's Catholic University, and an eyewitness to the atomic bomb attack on Hiroshima wrote:
"We have discussed among ourselves the ethics of the use of the bomb. Some consider it in the same category as poison gas and were against its use on a civil population. Others were of the view that in total war, as carried on in Japan, there was no difference between civilians and soldiers, and that the bomb itself was an effective force tending to end the bloodshed, warning Japan to surrender and thus to avoid total destruction. It seems logical to me that he who supports total war in principle cannot complain of war against civilians."
Some supporters of the bombings have emphasized the strategic significance of Hiroshima, as the Japanese 2nd army's headquarters, and of Nagasaki, as a major munitions manufacturing center. Some historians have claimed that U.S. planners wanted to end the war quickly to minimize potential Soviet acquisition of Japanese-held territory.
The Manhattan Project had originally been conceived as a counter to Nazi Germany's atomic bomb program, and with the defeat of Germany, several scientists working on the project felt that the United States should not be the first to use such weapons. Two of the prominent critics of the bombings were Albert Einstein and Leo Szilard, who had together spurred the first bomb research in 1939 with a jointly written letter to President Franklin D. Roosevelt. Szilard, who had gone on afterwards to play a major role in the Manhattan Project, argued: "If the Germans had dropped atomic bombs on cities instead of us, we would have defined the dropping of atomic bombs on cities as a war crime, and we would have sentenced the Germans who were guilty of this crime to death at Nuremberg and hanged them." In the days just before their use, many scientists (including American nuclear physicist Edward Teller) argued that the destructive power of the bomb could have been demonstrated without the taking of lives.
The existence of historical accounts which indicate that the decision to use the atomic bombs was made in order to provoke an early surrender of Japan by use of an awe-inspiring power, coupled with the observation that the bombs were purposefully used upon targets which included civilians, has caused some commentators to state that the incident was an act of state terrorism. Historian Robert Newman, who is in favor of the decision to drop the bombs, took the claim of state terrorism seriously enough to argue that the practice of terrorism is justified in some cases.
Some have claimed that the Japanese were already essentially defeated, and therefore use of the bombs was unnecessary. General Dwight D. Eisenhower so advised the Secretary of War, Henry L. Stimson, in July of 1945. The highest-ranking officer in the Pacific Theater, General Douglas MacArthur, was not consulted beforehand but said afterward that he felt that there was no military justification for the bombings. The same opinion was expressed by Fleet Admiral William D. Leahy (the Chief of Staff to the President), General Carl Spaatz (commander of the U.S. Strategic Air Forces in the Pacific), and Brigadier General Carter Clarke (the military intelligence officer who prepared intercepted Japanese cables for U.S. officials); Major General Curtis LeMay; and Admiral Ernest King, U.S. Chief of Naval Operations, Undersecretary of the Navy Ralph A. Bard, and Fleet Admiral Chester W. Nimitz, Commander in Chief of the Pacific Fleet.
Eisenhower wrote in his memoir The White House Years:
"In 1945 Secretary of War Stimson, visiting my headquarters in Germany, informed me that our government was preparing to drop an atomic bomb on Japan. I was one of those who felt that there were a number of cogent reasons to question the wisdom of such an act. During his recitation of the relevant facts, I had been conscious of a feeling of depression and so I voiced to him my grave misgivings, first on the basis of my belief that Japan was already defeated and that dropping the bomb was completely unnecessary, and secondly because I thought that our country should avoid shocking world opinion by the use of a weapon whose employment was, I thought, no longer mandatory as a measure to save American lives."
The United States Strategic Bombing Survey, after interviewing hundreds of Japanese civilian and military leaders after Japan surrendered, reported:
"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."
The survey assumed that continued conventional attacks on Japan—with additional direct and indirect casualties—would be needed to force surrender by the November or December dates mentioned.
In 1963 the bombings were subjected to judicial review in Shimoda et al. v. The State. On the 22nd anniversary of the attack on Pearl Harbor, the District Court of Tokyo declined to rule on the legality of nuclear weapons in general, but found that "the attacks upon Hiroshima and Nagasaki caused such severe and indiscriminate suffering that they did violate the most basic legal principles governing the conduct of war." In the opinion of the court, the act of dropping an atomic bomb on cities was at the time governed by international law found in the Hague Regulations on Land Warfare of 1907 and the Hague Draft Rules of Air Warfare of 1922–1923. and was therefore illegal.
Others contend that Japan had been trying to surrender for at least two months but the U.S. refused by insisting on an unconditional surrender. In fact, while several diplomats favored surrender, the leaders of the Japanese military were committed to fighting a "decisive battle" on Kyushu, hoping that they could negotiate better terms for an armistice afterward—all of which the Americans knew from reading decrypted Japanese communications. The Japanese government did not decide what terms, beyond preservation of an imperial system, they would have accepted to end the war; as late as August 9, the Supreme Council was still split, with the hardliners insisting Japan should demobilize its own forces, no war crimes trials, and no occupation. Only the direct intervention of the emperor ended the dispute, and even after that a military coup was attempted to prevent the surrender.
There is also some question as to how much Truman knew about the initial bombing. In his diary, he states that he told Secretary of War Stimson "to use it so that military objectives and soldiers and sailors are the target, not men, women, and children", and that they were in accord that "the target will be a purely military one". Immediately after the bombing, Truman gave a speech stating, "The world will note that the first atomic bomb was dropped on Hiroshima, a military base. That was because we wished in this first attack to avoid, insofar as possible, the killing of civilians," seemingly not realizing that Hiroshima was a major city.
Another criticism is that the U.S. should have waited a short time to gauge the effect of the Soviet Union's entry into the war. The U.S. knew, as Japan did not, that the Soviet Union had agreed to declare war on Japan three months after V-E Day; such an attack was indeed launched on August 8, 1945. The loss of any possibility that the Soviet Union would serve as a neutral mediator for a negotiated peace, coupled with the entry into combat of the Red Army (the largest active army in the world), might have been enough to convince the Japanese military of the need to accept the terms of the Potsdam Declaration (plus some provision for the emperor).
Because no U.S. invasion was imminent, it is argued that the U.S. had nothing to lose by waiting several days to see whether the war could be ended without use of the atom bomb. As it happened, Japan's decision to surrender was made before the scale of the Soviet attack on Manchuria, Sakhalin Island, and the Kuril Islands was known, but had the war continued, the Soviets had plans to invade Hokkaido well before the Allied invasion of Kyushu. Tsuyoshi Hasegawa's research has led him to conclude that the atomic bombings themselves were not the principal reason for capitulation. Instead, he contends, it was the swift and devastating Soviet victories on the mainland in the week following Stalin's August 8 declaration of war that forced the Japanese message of surrender on August 15, 1945.
A number of organizations have criticized the bombings of Hiroshima and Nagasaki on moral grounds. To give one example, a 1946 report by the Federal Council of Churches entitled Atomic Warfare and the Christian Faith, includes the following passage:
"As American Christians, we are deeply penitent for the irresponsible use already made of the atomic bomb. We are agreed that, whatever be one's judgement of the war in principle, the surprise bombings of Hiroshima and Nagasaki are morally indefensible."
Added by Sehrus June 25, 2006