Japan’s surprise attack on the U.S. naval base at Pearl harbor on December 7, 1941,began a decade of deteriorating relations between Japan and the United States and led to an immediate decleration of war from the U.S The Potsdam Declaration- on July 26, 1945 Allied leaders, called on Japan to surrender. if it did, it was promised a peaceful government. If it did not, it would face destruction. On August 14, 1945, Japan surrendered to the Allies, ending World War II.