Atomic Warfare

In mid-July 1945, as Allied forces prepared for the final assault on Japan, American scientists tested a secret weapon at an isolated desert site near Los Alamos, New Mexico. In 1942, Roosevelt had authorized the top-secret Manhattan Project to find a way to convert nuclear energy into a superbomb before the Germans added such a weapon to their arsenal. More than 100,000 Americans, led by scientists, engineers, and military officers at Los Alamos, worked frantically to win the race for an atomic bomb. Germany surrendered two and a half months before the test on July 16, 1945, when scientists first witnessed an atomic explosion that sent a mushroom cloud of debris eight miles into the atmosphere. After watching the successful test of the bomb, J. Robert Oppenheimer, the head scientist at Los Alamos, remarked soberly, “Lots of boys not grown up yet will owe their life to it.”

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President Truman saw no reason not to use the atomic bomb against Japan if doing so would save American lives. Despite numerous defeats, Japan still had more than 6 million reserves at home for a last-ditch defense against the anticipated Allied assault, which U.S. military advisers estimated would kill at least 250,000 Americans. But first Truman issued an ultimatum: Japan must surrender unconditionally or face utter ruin. When the Japanese failed to respond by the deadline, Truman ordered that an atomic bomb be dropped on a Japanese city. The bomb that Colonel Paul Tibbets and his crew released over Hiroshima on August 6 leveled the city and incinerated about 80,000 people, and many thousands more died later from injuries and radiation. Three days later, after the Japanese government still refused to surrender, the second atomic bomb killed nearly as many civilians at Nagasaki.

Major Campaigns and Battles of World War II, 1939–1945

September 1, 1939 Germany attacks Poland.
September 3, 1939 Britain and France declare war on Germany.
April 1940 Germany attacks Denmark and Norway.
May 1940 Germany invades Netherlands, Belgium, Luxembourg, and France.
June 1940 Italy joins Germany in war against Allies.
June–November 1940 Battle of Britain.
June 22, 1941 Germany invades Soviet Union.
December 7, 1941 Japan attacks Pearl Harbor.
December 8, 1941 U.S. Congress declares war on Japan.
December 11, 1941 Germany and Italy declare war on United States.
January 2–May 6, 1942 Battles of Bataan and Corregidor.
May 7–8, 1942 Battle of the Coral Sea.
June 3–6, 1942 Battle of Midway.
August 1942–February 1943 Battle of Guadalcanal.
August 21, 1942–January 31, 1943 Battle of Stalingrad.
October 23–November 5, 1942 British halt Germans at Battle of El-Alamein.
November 1942–May 1943 Allies mount North African campaign.
July 10, 1943 Allies begin Italian invasion through Sicily.
June 4, 1944 Allies liberate Rome from German occupation.
June 6, 1944 D Day—Allied forces invade Normandy.
August 25, 1944 Allies liberate Paris.
September 12, 1944 Allies enter Germany.
October 23–26, 1944 Battle of Leyte Gulf.
December 16, 1944–January 31, 1945 Battle of the Bulge.
February 19–March 16, 1945 Battle of Iwo Jima.
April 1–June 21, 1945 Battle of Okinawa.
May 2, 1945 Soviet forces capture Berlin.
August 6, 1945 United States drops atomic bomb on Hiroshima.
August 9, 1945 United States drops atomic bomb on Nagasaki.
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Hiroshima This photo shows part of Hiroshima shortly after the atomic bomb dropped from the Enola Gay, leveling the densely populated city. Deadly radiation from the bomb maimed and killed Japanese civilians for years afterward.
Bettmann/Corbis.

With American assurance that the emperor could retain his throne after the Allies took over, Japan surrendered on August 14. On a troopship departing from Europe for what would have been the final assault on Japan, an American soldier spoke for millions of others when he heard the wonderful news that the killing was over: “We are going to grow to adulthood after all.”

While all Americans welcomed peace, some worried about the consequences of unleashing atomic power. Almost every American believed that the atomic bomb had brought peace in 1945, but nobody knew what it would bring in the future.

REVIEW Why did Truman elect to use the atomic bomb against Japan?