The Potsdam conference was held on August 2nd, 1945, for the sake of drafting peace treaties with Germany's former allies. Out of all of them, Japan outright refused the declaration, but later agreed after, tragically, atomic bombs were dropped on Hiroshima and Nagasaki. This was a ploy by the United States government in order to force the Japanese to surrender, becoming the first AND only nation to ever use nuclear weapons in combat.
