Lesson Plan on Mass Casualties
and Making Decisions About War
Basic Facts on the Decision to End WWII
by Attacking Japan with Atomic Bombs
The decision to end World War II with surprise atomic bomb attacks on Japanese cities is still very controversial. Some claim that the atomic bombings helped force a quick end to the war and that the example served to intimidate the Russians throughout the Cold War, helping to keep the peace. Pointing to occasions when the U.S. and Russia (the Soviet Union) pulled back from the brink of nuclear holocaust, they assert that the high death toll, horrific injuries and massive destruction at Hiroshima and Nagasaki helped leaders of the U.S. and the Soviet Union realize that nuclear war should be avoided at almost any cost.
Opponents of the use of the bomb note that as of August 1945, Japan had already lost the war. They contend that, especially with the entry of Russia into the Pacific war, Japan would have surrendered within a few weeks or months even without the atomic attacks. They point to the alternatives to surprise atomic attacks on Japanese cities, such as a demonstration explosion, atomic bombing of large military installations, or simply waiting for Japan to collapse, as more humane ways to end the war. The atomic bombings, they assert, caused the unnecessary deaths of more than 300,000 human beings, escalated the violence level of warfare by establishing a precedent for the use of atomic weapons, and undercut the moral authority the U.S. had in the world.
If we are to learn from the past we must analyze it fearlessly and find the truth where it lies. Otherwise we cannot improve the decisions our governments make, and, if there were mistakes, we will be condemned to repeat them. In that spirit, this handout sets out some of the facts relating to the situation that faced the U.S. and Japan in the summer of 1945.
1. World War II was started by Japan, Germany and Italy (the Axis countries) each controlled by fanatic fascist dictatorships. These governments had little regard for the welfare of their own people or of their opponents. WWII was the bloodiest war in history, causing the deaths of 40 - 50 million people, including 292,000 U.S. soldiers and sailors killed in combat and another 115,000 servicemen killed from non-battle related causes. More than 600,000 U.S. servicemen were wounded. (The only war with more American casualties was the Civil War in which American soldiers fought and died in large numbers on both sides.)
2. The Axis powers waged war with a viciousness beyond anything previously seen by modern man. Early in the war, Germany attacked civilian populations. The Japanese devastated civilian populations in China, made a surprise attack on Pearl Harbor, used tactics such as kamikaze planes, and treated POWs brutally.
3. WWII was a "total war" in which most of the resources of the combatant nations were utilized for the war effort. For example, the Japanese government ordered civilians, including women and children, to work in munitions factories and military offices and to fight against any invading force. The Allies also had women working in munitions factories and military offices.
4. An atomic bomb is a weapon of mass destruction which kills and injures people and destroys or damages structures over large areas. When dropped on an urban area, an atomic bomb will kill tens of thousands of people and destroy the infrastructure of the city including families, neighborhoods, schools, hospitals, etc. The destruction occurs instantaneously and does not discriminate between combatant or non-combatant, guilty or innocent, young or old, resident or visitor, imprisoned or free. Finally, atomic bombs cause radiation poisoning which sickens people for years and affects all living organisms in the area exposed. Atomic bombs are the most powerful weapons of terror invented by mankind.
5. Hiroshima and Nagasaki were cities primarily inhabited by civilians. However, since Japan had been mobilized for total war, the U.S. government regarded both cities as active working parts of the Japanese war effort. In addition, Hiroshima was the headquarters of the Japanese Army defending southern Japan, and was a major military storage and assembly point. By August 1945, there were between 25,000-50,000 servicemen in the city, as well as munitions and supply depots and thousands of Koreans pressed into slave labor by the Japanese. It contained a massive Mitsubishi factory, a gun factory producing 6,000 rifles a week, and businesses that made parts for kamikaze airplanes. Nagasaki was an important seaport and contained several large industrial plants of wartime importance.
6. The official policy of the U.S. and its allies was that they would vigorously prosecute the war until they had secured the "unconditional surrender" of the Axis powers.
7. By 1945, the use of air power to destroy civilian targets was an established U.S. policy. A firestorm is a fire of such great size and intensity that it generates and is fed from all sides by strong inrushing winds. Sometimes the winds drawn into a firestorm have the force of a hurricane. In the European theater the Allies had caused firestorms in two German cities, killing an estimated 30,000 to 40,000 civilians in each raid. Japanese air defenses were so ineffectual by 1945 that the U.S. Twentieth Air Force bombed at will. On March 9, 1945, using incendiary weapons, U.S. bombers started a firestorm that incinerated sixteen square miles of Tokyo, killing more than 83,000 people, injuring more than 40,000, and leaving up to one million homeless. This was the single most destructive air raid in history (even more destructive than the atomic bomb attacks on Hiroshima and Nagasaki). The March 9 raid on Tokyo was followed by other incendiary raids on that city and attacks by air on other major Japanese population centers. Between March and July more than 60 Japanese cities were devastated by conventional bombing. In July 1945, for example, Twentieth Air Force long range B-29 bombers flew 6500 sorties dropping 42,000 tons of bombs and mines. By then, the U.S. could send 800 B-29s on simultaneous operations.
8. On May 8, 1945, Germany surrendered unconditionally to the Allies. The powerful armies, navies and air forces that the U.S. and Britain had used to smash Germany's power in Western Europe were being transferred to the Pacific to augment the attack on Japan.
9. By mid-1945 it was clear to everyone, except the most fanatic militarists, that Japan could not win WWII. The U.S. Navy had imposed an effective blockade cutting off the oil and raw materials necessary to wage war. Japan's Navy had been reduced to a mere harrying force. Its Air Force could only mount kamikaze, or suicide, attacks. Its Army had suffered defeat after defeat by the United States Army and Marines. Japanese military assets were limited to: (1) the ability to inflict damage with kamikaze attacks and (2) the vast size of the Japanese Army which had approximately 5,000,000 men under arms in Japan, China, Korea, the Pacific Islands, and Indo-China. Most of these soldiers, like the defenders of Okinawa, subscribed to the samurai code of death before surrender. Many in the Japanese military preferred the annihilation of the Japanese nation to surrender.
10. In June of 1945, Okinawa, considered to be the gateway to the Japanese Home Islands, fell to U.S. forces. Japanese soldiers had resisted almost to the last man. 90,000 died out of a force of 100,000. They also enlisted the inhabitants of the island to fight the U.S. and 100,000 civilians lay dead. The 12,000 Allied deaths in the Okinawan campaign were considered to be very high.
11. The fanatic militarists who still dominated the Japanese government argued that through kamikaze attacks by plane, boat, frogmen and suicide bombers, and by mobilizing the army and the population to fight to the death, they could either throw back a U.S. invasion and turn the tide of the war, or cause such severe casualties that Japan would be able to negotiate beneficial terms. However, some among the ruling elite realized, even before the atomic bombing, that Japan had lost the war. They wanted to end the war quickly to stop the loss of life and destruction of property. But they were intimidated by the military fanatics who, for more than a decade, had used arrest and assassination against their political opponents.
12. On June 8, the military's proposal to risk all in one final fight to the death on the shores of the Home Islands was approved by the Emperor. However, under pressure from the end-the-war faction, Japan also began to seek Russian help in mediating a surrender, although on terms acceptable to the military. (In WWII, Russia was an ally of the U.S. and England in the war in Europe. Russian and Japan had signed a neutrality treaty in 1941 because even the military fanatics knew that Japan could not win a war against Russia while still fighting the U.S. and Great Britain. Russia needed peace in Asia so that it could concentrate it efforts on resisting an expected German invasion.)
13. The citizens of the U.S. were very angry at Japan and considered its leaders to be war criminals. They wanted the war and the deaths of Allied soldiers to end. Franklin D. Roosevelt, who had led the U.S. out of despair during the Great Depression and to the brink of victory in WWII, had died in April. He was succeeded by Harry S. Truman, an as yet untested leader, committed to following Roosevelt's policies. Those policies included a demand for "unconditional surrender" and the effort to end the war as soon as possible. It took Truman several months to learn his job and fully grasp the reigns of government. It was during these months that the decision on whether to attack Japan with atomic bombs was made.
14. While in late July and August the pace of combat operations was reduced and there were fewer U.S. casualties, soldiers and sailors were still dying virtually every day, sometimes in large numbers. For example, on July 29, a U.S. navy ship, the Indianapolis, was torpedoed by a Japanese submarine and 883 lives were lost. The worst case scenario for the U.S. was invasion of the Japanese Home Islands. The estimates of U.S. casualties in an invasion varied widely. Mid-range estimates projected 100,000 U.S. soldiers and sailors killed. Some estimates were much higher, approaching one million casualties (deaths and injuries). It was estimated that probably more than a million Japanese soldiers and civilians would be killed in an invasion in combat or from illness or starvation.
15. In 1942, fearful that Germany would develop an atomic bomb, the U.S. had embarked on a crash program to invent the weapon first. The Manhattan Project cost two billion dollars, an enormous sum in those days. It was a terrific gamble because no one really knew for sure that it would work. The first successful test of an atomic explosion occurred on July 16, 1945. The power and destructiveness of the test were beyond the expectations of the scientists. A steel and concrete tower 1/2 mile from the place of detonation was ripped out of its foundation and lay a twisted ruin on the desert floor. After that test, the U.S. knew that if it could make an atomic bomb explode in a city, tens of thousands of people would probably die. However, there was no absolute assurance that all of the complicated mechanisms for an atomic bomb to detonate at the right time on the intended target could be made to work in combat conditions.
16. The factor of the Soviet Union, at that time led by Josef Stalin, was important to both the U.S. and Japan. U.S. policy was to get the Soviet Union into the war against Japan as soon as possible. This would open another front and put tremendous pressure on the Japanese.
17. In 1945 Russia began setting up puppet regimes in Eastern Europe in violation of its agreements with the U.S. and Great Britain concerning the make-up of postwar Europe. After the defeat of Germany, the U.S. and Britain began moving their European armies to Asia to finish off Japan. However, massive forces of the Red Army remained in Europe. Churchill (the great wartime leader of Great Britain) and Truman understood that the reduced strength of U.S. and British troops in Europe would make the Russians even harder to handle. The U.S. needed some counterweight to the strength of the Red Army. The atomic bomb, along with the knowledge that the U.S. was willing to use it, was just such a counterweight and would go a long way toward making Stalin more reasonable. Thus, while the U.S. wanted Russia to attack Japan, it didn't want Russia to be so involved in the war in Asia that Russia earned the right to participate in the postwar occupation. The U.S. didn't want a repeat of the troubles that the Allies were experiencing in postwar Europe to be carried over into Japan.
18. Before the end of WWII the Japanese considered their Emperor to embody the divine spirit of the Japanese people. He was seen as the nation's link with heaven and was a symbol of national unity. Even those members of the Japanese government who advocated an immediate end to the war sought guarantees that the Emperor would continue as the head of the Japanese government in the postwar period. Moreover, he was the patron of the ruling elite who had led Japan into the war. They would need the Emperor's protection from reprisals in the postwar period. The military, in addition to insisting upon the retention of the Emperor and the imperial system, demanded three other conditions to any surrender: limitations the occupation, war criminals to be tried in Japanese courts, and to have the Japanese army disarm itself.
19. Many officials in the U.S. government believed that the Japanese would fight almost to the last man to preserve the institution of the monarchy and to protect the Emperor. They argued also that only an Emperor cooperating with U.S. occupying forces could order the 5,000,000 man Japanese armed forces to surrender without bitter fighting. Otherwise, the armed forces would resist to the last man and there would be terrible casualties on both sides. They argued that the U.S. should define unconditional surrender to mean that the Emperor could stay if desired by the Japanese people. Others opposed an early commitment to keeping the Emperor pointing to the fact he was a war criminal and that the interests of justice required that he be deposed and prosecuted. They also contended that the continuation of the imperial system in Japan would hamper the efforts to democratize Japan.
20. On July 26, the U.S., Britain, and China issued the Potsdam Proclamation. The document offered Japan liberal surrender terms but insisted that war criminals would be prosecuted and that "there must be eliminated for all time the authority and influence of those who have deceived and misled the people of Japan into embarking on world conquest ...." The Proclamation also said that the Allies would accept a "peacefully inclined and responsible government" chosen by the Japanese people. The Allied statement threatened Japan with "prompt and utter destruction" if its terms were not accepted without delay. There was no mention of a revolutionary new weapon to be employed against Japan if the war continued. At the Potsdam Conference, Stalin promised Truman that Russia would attack Japanese positions in Manchuria by August 15. Truman was elated.
21. The Japanese Prime Minister and the Japanese military saw the generous terms of the Potsdam Proclamation as a sign of weakness by the U.S. The Japanese government responded to the Potsdam Proclamation by claiming it was simply a rehash of old Allied positions and stated that it would be treated with silent contempt. In the 10 days between the Potsdam Proclamation and the bombing of Hiroshima, the Japanese government did not seek clarification of the possible opening in the Potsdam Proclamation that would protect the Emperor if the Japanese people wanted to keep him. During that 10 day period, more than 10,000 Japanese died from Allied conventional air raids. Japan's rejection of the Potsdam Proclamation triggered the U.S. decision to proceed with the atomic attacks.
22. The U.S. had the following alternatives to ending the war: (1) invade (scheduled for November); (2) continue to bomb with conventional weapons and enforce the blockade in the hope that the added pressure of the Russian attack would make the militarists agree to surrender; (3) add pressure by attacking Japan with atomic weapons; (4) attempt to open negotiations by, for example, agreeing in advance to permit the Emperor to remain as the head of the Japanese government.
23. There were five alternative methods of using the bomb that received consideration: (1) targeting rail and communications infrastructure, military installations, and troop concentrations to soften up resistance to the invasion; (2) a demonstration over but not on Japanese territory with international observers present followed by the threat of using bombs on Japan itself; (3) an attack on a purely military target, such as the remnants of the Japanese fleet or a large military base, followed by the threat of using bombs on cities; (4) bombing cities with warning; and (5) bombing cities without warning. (Note that the U.S. had only two atomic bombs after the Alamogordo test. Nuclear fuel is difficult to produce. Fuel for another six bombs could be made by November 1, the date set for the invasion. The third atomic bomb was expected to be available later in August.)
24. There were disadvantages to each of the possible ways to use a bomb. A few are set out below. The Japanese government would probably not tell its people about a demonstration nor would they believe that we could make the bomb explode under combat conditions. Thus, one of the two bombs that we had would have been wasted. Using the bomb on cities held out the certainty of civilian casualties. (But U.S. policy at the time did not hold that civilian casualties should be avoided.) Advance notification of several locations on which the bomb might be dropped gave the Japanese the opportunity to move some of the tens of thousands Allied prisoners of war who were imprisoned in Japan to those locations. It also gave Japan the opportunity to concentrate what air defenses the Japanese retained to those locations. The U.S. had very few atomic bombs (only two at that time) and if one didn't work for some reason, the threat of multiple bombs would have to wait until later in August.
25. The first atomic bomb (nicknamed "Little Boy") was dropped without warning on Hiroshima on August 6, 1945. 255,000 people were in the city and some 66,000 (26%) died instantly or within the next four months with 69,000 (29%) being injured. Burns accounted for 60% of the injuries and falling debris accounted for 30%. Note that other estimates are higher both in terms of total population. For example, tens of thousands of Korean slave laborers in the city were probably not counted. Within the four square miles of the city of Hiroshima, 48,000 out of 76,000 buildings were completely demolished. Ninety percent of the city's doctors and nurses were killed, so that the injured who managed to drag themselves to the hospitals often lay untreated and, because of their horrific burns, unrecognized. Many people had the experience of having the person walking beside them seem to disappear. Indeed, some were so totally vaporized that only their shadows remained on the walls. The government in Tokyo knew that the "whole city of Hiroshima was destroyed by a single bomb" the next day.
26. In the days that followed the atomic explosions, the U.S. continued air raids using conventional weapons. Some of these were massive and one employed more than 1,000 B-29s.
27. By the time of the first atomic bombing, the Japanese effort to obtain Russian mediation had failed. However, even after the shock of the atomic attack on Hiroshima, the Japanese government neither submitted a counter proposal to the Potsdam Proclamation nor did it seek direct negotiations with the United States.
28. Early in the morning of August 9, the Soviet Union declared war on Japan and Soviet troops attacked Japanese positions in Manchuria. The Japanese armed forces immediately understood this to be a devastating development. The Japanese defense in Manchuria, depleted by transfers to the Home Islands in preparation for the defense of the invasion, could not repulse the Russian attack. This was an additional shock to the Japanese rulers. When Japanese Prime Minister Suzuki learned that the Red Army was overrunning large amounts of territory, he reportedly said, "Is the [Japanese Army in Manchuria] that weak? Then the game is up."
29. There was no consideration by the U.S. about whether one bomb was enough. The U.S. did not wait for the Japanese government to digest the fact that the Soviet Union had attacked its positions in Manchuria before dropping a second atomic bomb and destroying another city. At about 11:00 a.m. on August 9 (several hours after Soviet troops attacked Japanese positions in Manchuria), the "Fat Man" atomic bomb was dropped on Nagasaki, killing another 40,000 people immediately (eventually 140,000 died from this blast). The Nagasaki atomic bombing was immediately reported to Tokyo.
30. The militarists continued to hold out for the additional conditions but on August 10 the Emperor decided to accept Potsdam surrender terms with one condition, that they did not "prejudices the prerogatives of His Majesty as a Sovereign Ruler."
31. By the time the U.S. received the Japanese note seeking one condition to the Potsdam terms, President Truman had received detailed reports and photographs from Hiroshima. He did not want to use a third atomic bomb solely for the purpose of deposing Hirohito. He told his cabinet that the thought of killing another 100,000 people -- many of them children -- was too horrible. However, the U.S. did not want to be seen backing down from the demand for "unconditional surrender."
32. The next day the U.S. replied. The note from President Truman stated that "From the moment of surrender the authority of the Emperor and the Japanese Government to rule the state shall be subject to the Supreme Commander of the Allied powers who will take such steps as he deems proper to effectuate the surrender terms." The reply stated that the Emperor would be required to ensure the surrender and "issue his commands to all the Japanese military, naval and air authorities" to lay down their arms. This implied that the Emperor would continue at the head of the Japanese government, at least for a time. The reply, however, reiterated the Potsdam term that "The ultimate form of government of Japan shall, in accordance with the Potsdam Proclamation, be established by the freely expressed will of the Japanese people."
33. The U.S. reply disappointed the Japanese government and the military wanted to continue the war. However, the Japanese Foreign Ministry intentionally mistranslated a key portion of Truman's reply to make it appear that the U.S. was agreeing to acknowledge the Emperor and continue him on the throne. On August 14, 1945, the Emperor accepted the U.S. terms and, at his request, this was ratified by the Japanese Cabinet.
34. By mid-1945, the Japanese government was receiving reports that a substantial number of Japanese citizens were disillusioned with the war and with their leadership, including the Emperor. The government and ruling elite feared a revolution that would totally destroy the emperor system and the ruling elite. Some in the Japanese ruling elites saw the atomic bombings as heaven-sent because it gave them a way to deflect criticism of their actions during the war. After all, no one can defend against an atomic bomb. Other Japanese focused on the help that the atomic bombings gave them in their political struggle with the militarists.
35. To prevent the surrender, diehard elements of the military attempted a coup d'etat. Initially, the top military figure in Japan, the War Minister, did not stop their activities and gave them friendly advice. Goon squads led by military officers sought to murder end-the-war advocates. The plotters were able take control of the Imperial Guard but eventually they were restrained by saner elements in the military.
36. While not committed to retaining the Emperor at the time of the armistice, the U.S. decided soon thereafter that the Emperor would be helpful in the peaceful surrender of Japanese forces and during the occupation of Japan. In return for his cooperation with the U.S. authorities, the Emperor was able to retain his throne and escape prosecution as a war criminal. The U.S. and Japanese governments conspired to suppress evidence of Hirohito's participation in the decisions that brought about the war.
37. After the U.S. had displayed the will to use the bomb, the power of the vast Red Army was checked in Europe and in Asia. The benefits lasted throughout the Cold War and even after the Soviets developed their own atomic weapons. One of the reasons that the U.S. was able to reduce its armies and keep defense spending to manageable levels during the Cold War (1945 - 1991) was the existence of its nuclear deterrent and the realization by the Soviets that the United States would use it.
38. On the several occasions after WWII that the world came to the brink of nuclear war the experience of Hiroshima and Nagasaki hung over deliberations and restrained world leaders. For example, even in the darkest days of the Korean War, President Truman never even considered using atomic weapons a second time. Another example is the Cuban Missile Crisis. See Learning Guide to "Thirteen Days". After the end of WWII, President Truman recognized that atomic bombs were weapons of terror. He said that a nuclear bomb isn't a "military weapon. ... It is used to wipe out women and children and unarmed people, and not for military uses."
Last updated April 11, 2008.