Harry S. Truman
Nazi Germany surrendered less than a month after Truman became president. This ended the war in Europe. However, the Japanese kept fighting. The Allies of World War II made the Potsdam Declaration, telling Japan to surrender or it would face "prompt and utter destruction." Japan did not surrender, so Truman ordered the first atomic bomb to be dropped on Hiroshima, Japan, on August 6th, 1945. Three days later, Truman ordered the second atomic bomb to be dropped on Nagasaki, Japan. Japan surrendered and the war ended.