Which leader is primarily associated with the announcement of the Manhattan Project's success?

The leader primarily associated with the announcement of the Manhattan Project's success is Harry S. Truman. After taking office in April 1945, Truman was informed about the atomic bomb and its actual development. Following the successful detonation of the first atomic bomb during the Trinity Test on July 16, 1945, Truman made the decision to use the bomb against Japan to hasten the end of World War II. He announced the bombing of Hiroshima on August 6 and Nagasaki on August 9, 1945, effectively communicating the success of the Manhattan Project and its implications for the war and future international relations.

Franklin D. Roosevelt, while instrumental in the project's inception, had already passed away by the time of its success. Winston Churchill and Joseph Stalin, although significant figures in World War II, were not primarily associated with the announcement of the project’s success; their roles were more related to military and political alliances during the war rather than the specifics of the atomic bomb’s development and its use.