Which U.S. president announced Japan's surrender in a radio address?

Harry S. Truman announced Japan's surrender in a radio address on August 14, 1945.

Truman became president after Franklin D. Roosevelt died on April 12, 1945. As president, he oversaw the final months of the war against Japan, including the atomic bombings and the Allied demand for unconditional surrender in the Potsdam Declaration.

His announcement came after Japan informed the Allies that it accepted the declaration, subject to preserving the authority of Emperor Hirohito. Truman told the American public that the war was over, while the formal legal surrender still had to be signed.

The announcement occurred on August 14 in the United States, while Japan's surrender broadcast aired on August 15 in Japan. The date difference explains why V-J Day appears as both August 14 and August 15 in historical references.