Why was US President Truman "on the high seas" when the Hiroshima atomic bomb was dropped?

Question

From the New York Times, August 7 1945. [First Atomic Bomb Dropped on Japan; Missile Is Equal to 20,000 Tons of TNT; Truman Warns Foe of a 'Rain of Ruin'](http://www.nytimes.com/learning/general/onthisday/big/0806.html) > The first news came from President Truman's office. Newsmen were > summoned and the historic statement from the Chief Executive, who still > is on the high seas, was given to them. Why was he on the high seas at this moment? Was he on an important trip or a mission?

Answer 1

Truman was actually traveling both during he first Trinity test *and* the Hiroshima bomb (one on the way to Europe and one on the way back) back and forth from the Potsdam conference. It was at that conference where, with the knowledge of his new weapon fresh in his mind, Truman and the other Allies made the Potsdam Declaration demanding Japanese surrender “without delay.” By the time the Japanese had rejected (for now, anyway, as the Emperor would later accept them) those terms and a working weapon assembled and sent to the front, Truman was on the way back home (by ship, naturally, as FDR had done for previous conferences).