The presidency of Harry S. Truman began on April 12, 1945, when Harry S. Truman became President of the United States upon the death of Franklin D. Roosevelt, and ended on January 20, 1953. Although Truman was told briefly on the afternoon of April 12 that the Allies had a new, highly destructive weapon, it was not until April 25 that Secretary of War Henry Stimson told him the details of the atomic bomb, which was almost ready. Germany surrendered on May 8, 1945, ending the war in Europe. Truman's attention turned to the Pacific, where he hoped to end the war as quickly, and with as little expense in lives or government funds, as possible. The United States Atomic Energy Commission, directed by David E. Lilienthal until 1950, was in charge of designing and building nuclear weapons under a policy of full civilian control.