During the spring and summer of 1945, the Big Three met for a second time, at the Yalta Conference, to decide the shape of the postwar world. Two months after the Yalta conference, Roosevelt was dead (April 12, 1945) and it was left to Harry Truman to bring the United States to victory in Europe and against Japan. While Nazi Germany collapsed in May, fighting in the Pacific was some of the heaviest in the war and American casualties were mounting. The prospect of even higher causalities prompted the United States to use a new weapon — the atomic bomb — to bring the war against Japan to an end.
The Yalta Conference. At Yalta, a resort on Russia's Crimean coast, Roosevelt, Churchill, and Stalin agreed to divide Germany into four zones of occupation, with France, Great Britain, and the United States in the west and the Soviet Union in the east. Although entirely within the Russian zone, Berlin would be administered by all four powers. The same arrangement would apply to Austria and Vienna. Stalin insisted that Russia keep the Polish territory it had occupied between 1939 and 1941 and suggested compensating Poland for its losses with German lands in the west. While he agreed in principal to holding free elections in Eastern Europe, Stalin supported the pro‐Communist government that was running Poland at the time and also demanded “friendly states” on the borders of the USSR. Roosevelt appreciated that it would be difficult to ensure a noncommunist Eastern Europe with Soviet troops on the ground but was willing to make concessions to ensure that the Russians would join in the war against Japan. Stalin confirmed at Yalta that the Soviet Union would declare war on Japan two or three months after Germany's surrender.
The defeat of Germany. The Germans launched a major offensive in the weeks before Christmas 1944 in the Ardennes Forest in France. This offensive, the Battle of the Bulge (December 16–January 16), proved only a short‐lived success, however, and British and American forces soon pushed into Germany from the west while the Russians advanced from the east. By the end of April, American and Soviet troops met at the Elbe River, and the battle for Berlin was in its final days. Adolph Hitler committed suicide in his bunker under the city on April 30, and the German military unconditionally surrendered to the Allies on May 8, 1945.
As the war in Europe ended, delegates from 50 countries met in San Francisco to create the United Nations. The structure of the new international organization, whose charter was signed in June 1945, included the General Assembly, in which each member state had a vote. At Stalin's insistence, Roosevelt and Churchill agreed at Yalta to give the Soviet Union three seats — one for the USSR and one each for the republics of Belorussia and the Ukraine. The General Assembly was little more than a forum for discussing world issues, however, and the additional votes had little impact. Responsibility for maintaining peace fell to the Security Council, in which the five permanent members — China, France, Great Britain, the Soviet Union, and the United States — have veto power. In addition, the charter provided for a number of agencies under the U.N. umbrella, such as the International Court of Justice and the United Nations Educational, Scientific, and Cultural Organization (UNESCO).
Decision to drop the bomb. American troops in the Pacific faced a difficult fight as the war moved closer to the Japanese islands. The battle of Iwo Jima (February–March 1945) cost U.S. Marines more 20,000 casualties. During the three‐month battle for Okinawa (April–June 1945), only 350 miles from Japan, 12,000 Americans were killed and 36 wounded. Attacks by Japanese suicide planes, the kamikaze (or “divine wind”) caused the heaviest damage ever to the U.S. Navy. The invasion of Japan itself, which was being planned for late 1945, would mean even greater losses, perhaps as many as a million men, according to some estimates. These circumstances were the context in which the decision to use the atomic bomb was made.
The result of a scientific, technical, and industrial program known as the Manhattan Project, the first atomic bomb was successfully tested in Alamogordo, New Mexico, on July 16, 1945. President Truman received word about the test as he met with Stalin and British Prime Minister Clement Atlee (who had replaced Churchill due to the Labour Party victory in the 1945 parliamentary elections) at the Potsdam Conference, held in a suburb of Berlin. The United States and its Allies issued the Potsdam Declaration (July 26) that promised “prompt and utter destruction” if Japan did not unconditionally surrender — an ultimatum Japan rejected on July 29. An atomic bomb was used against Hiroshima on August 6, completely destroying four square miles of the city and killing more than 70,000 people upon impact. A second bomb was dropped on Nagasaki three days later, causing 40,000 deaths. Emperor Hirohito, long a figurehead in Japanese politics, then insisted on surrender. The Japanese agreed to Allied terms on August 14, thus ending World War II.
The decision to use an atomic bomb has long been and continues to be controversial. Historians argue that by the summer of 1945, Japan was on the verge of collapse, and the continued air attacks would have led to surrender. Some claim that the real reason the bombs were used was as a show of American strength for the Soviet Union, a theory that would make Hiroshima the first salvo of the Cold War, the icy U.S.–Soviet rivalry that followed World War II. Others maintain that racism was a factor, insisting that the bomb would never have been used against Germany, for example. Scientists who worked on the Manhattan Project wanted, in fact, to demonstrate the destructive force of the bomb for the Japanese military in one more test, hoping that witnessing the power the United States could unleash would cause Japan to surrender. In the end, however, the fact remains that Japan refused to surrender. Faced with the possible loss of tens of thousands of American troops in an invasion, Truman and his military advisors were determined to use every weapon available. Truman noted that the bomb ended the war quickly and that in so doing, it saved not only American lives but Japanese as well.