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Basic Information on the Bomb
Source: The Enola Gay Exhibit (no longer online) 8/11/98.

The firebombing campaign, which began in earnest with the great raid against Tokyo on the night of March 9-10, proved far more devastating than expected. During the next five months, [US Air Force Secretary] LeMay's bombers razed one half of the total area of 66 cities—burning 178 square miles.  By the summer of 1945, Japan's productive capacity had been lowered as follows:  power generation by 50 percent, oil by 85 percent, and overall industrial production by 60 percent. The destruction was so complete LeMay warned his superiors he would run out of targets by September.

On April 5, l945, one week before Roosevelt's death, Japanese Prime Minister Kuniaki Koiso and his cabinet resigned because of the increasingly disastrous course of the war—the second such resignation in less than a year. A peace faction in the military-dominated Japanese government had begun to realize that a way had to be found to negotiate an end to the war. The Allied demand for "unconditional surrender " was, however, regarded as intolerable.

A key obstacle to any Japanese surrender was the Emperor's position. To the Japanese warlords, the Allied demand for unconditional surrender meant the total destruction of their political system, including a "divine" monarchy that had survived for more than a thousand years.  To most Americans, [Emperor] Hirohito was a hated symbol of Japanese military aggression. Many wanted him executed, or at least imprisoned or exiled. Undersecretary of State Joseph Grew nonetheless argued that the Japanese might surrender if allowed to retain their Emperor. He also asserted that the Emperor would be "the sole stabilizing force" capable of making the Japanese armed forces accept a surrender order.

This passage [from the official minutes of the Interim Committee meeting of May 31, 1945] gives the committee's recommendation regarding the use of the bomb:
             Secretary [Stimson] expressed the conclusion, on which there
             was general agreement, that we could not give the Japanese any
             warning, that we could not concentrate on a civilian area;
             but that we should seek to make a profound psychological
             impression on as many inhabitants as possible. … [T]he Secretary
             agreed that the most desirable target would be a vital war plant
             employing a large number of workers and closely surrounded by
             workers' houses.

Estimates of the number of American casualties—dead, wounded, and missing—that the planned invasion of Japan would have cost varied greatly. In a June 18, 1945, meeting, General Marshall told President Truman that the first 30 days of the invasion of Kyushu could result in 31,000 casualties. But Admiral Leahy pointed out that the huge invasion force could sustain losses proportional to those on Okinawa, making the operation much more costly. Had the Kyushu invasion failed to force Japan to surrender, the United States planned to invade the main island of Honshu, with the goal of capturing Tokyo.  Losses would have escalated.

After the war, Truman often said that the invasion of Japan could have cost half a million or a million American casualties.  The origin of these figures is uncertain, but Truman knew that Japan had some two million troops defending the home islands.  He believed, along with the many Americans who would have had to invade Japan, that such a campaign might have become, in his words from June 18, 1945, "an Okinawa from one end of Japan to the other."  Added to the American losses would have been several times as many Japanese casualties—military and civilian.  The Allies and Asian countries occupied by Japan would also have lost many additional lives.  For Truman, even the lowest of the casualty estimates was unacceptable.  To prevent an invasion and to save as many lives as possible, he chose to use the atomic bomb.

President Truman believed that an invasion of Japan would be necessary if the atomic bomb did not work.  In hindsight, however, some have questioned whether an invasion was inevitable.  Based on information available after the war, the U.S. Strategic Bombing Survey concluded in 1946 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 U.S. naval blockade was strangling Japan, which depended totally on imported fuel, while conventional bombing was destroying its infrastructure.

However, other postwar observers, including Secretary Stimson, doubted that Japan's rulers would have accepted unconditional surrender if the home islands had not been invaded or if the atomic bomb had not been dropped.  In any case, many American lives would have been lost by November 1, 1945, and after that date, the invasion of Kyushu would have been in full swing.

After a devastating defeat in the three-day battle of Leyte Gulf in October 1944, Japanese leaders introduced a new weapon:  kamikaze or suicide pilots.  The word kamikaze literally means "divine wind" after a typhoon in the 13th century that kept Kublai Khan's invading forces at bay.  Author Daniel Yergin says that Kamikaze pilots "were meant to be the ultimate embodiment of the Japanese spirit, inspiring all their compatriots to total sacrifice.  But," he further points out, "they also served a very practical purpose for a country extremely short of oil, planes, and skilled pilots. ... Not only was the pilot sure to cause more damage if he crashed his plane, not only would his commitment and willingness to die unnerve an enemy who could not comprehend the mentality of such an act, but--since he was not going to return--his fuel requirement was cut in half."  Daniel Yergin, The Prize:  The EpicQuest for Oil, Money & Power, p. 362.