He started with a burst of decisions. After being sworn in on April 12, he decided to proceed with the United Nations organizing conference April 25 in San Francisco. In a radio speech to the nation, given before a joint session of Congress on April 16, Truman promised to pursue FDR's objective of unconditional surrender by Germany and Japan. He retained Roosevelt's cabinet. Every night in the White House, Truman read endless memos and files to ready himself for the choices he was facing. He gave particular emphasis to foreign affairs in preparation for his upcoming conference in Potsdam with Winston Churchill of the United Kingdom and Joseph Stalin of the Soviet Union.
Shortly after Truman took office, Germany did surrender unconditionally, but Japan fought on. Thirteen days after taking office, on April 25, Truman received a detailed briefing from Secretary of War Henry Stimson on the development of the atomic bomb. On July 25, after he was informed that the first test of the weapon had shown its enormous destructive force, he confirmed an order to use the bomb against Japan. He wanted to force Tokyo to surrender unconditionally and to spare the United States from making what his military planners said would be a horrendously costly invasion of the Japanese homeland. "I could not bear this thought," Truman said, "and it led to the decision to use the atomic bomb." The bombs were dropped on Hiroshima August 6 and Nagasaki August 9. An estimated 150,000 civilians died. The Japanese surrendered August 14.
There were many other problems—how to contain the aggressive and recalcitrant Soviet Union, how to deal with a civil war in China, how to construct the postwar world, how to rebuild the American economy in peacetime. It wasn't long before Truman fully realized the burdens he carried, and he started referring to the White House as the "big white jail." On another occasion, he said, "Being a president is like riding a tiger. You have to keep on riding or be swallowed."
But in his first 100 days, he showed his decisiveness, his intelligence, and his personal sense of duty. And those became the hallmarks of the Truman era.