Japanese foreign affairs minister Mamoru Shigemitsu signs the Japanese Instrument of Surrender on board USS Missouri as General Richard K. Sutherland watches, September 2, 1945. On August 6, 1945, the United States dropped an atomic bomb on the city of Hiroshima. Late in the evening of August 8, 1945, in accordance with the Yalta agreements, but in violation of the Soviet-Japanese Neutrality Pact, the Soviet Union declared war on the Empire of Japan, and soon after midnight on August 9, 1945, the Soviet Union invaded the Imperial Japanese puppet state of Manchukuo. Later that day, the United States dropped another atomic bomb, this time on the city of Nagasaki. The combined shock of these events caused Emperor Hirohito to intervene and order the Big Six to accept the terms for ending the war that the Allies had set down in the Potsdam Declaration.