Attack on Pearl HarborJapanese airplanes made a surprise attack on the US Navy in Pearl Harbor. Hundreds of Japanese attacked. The bombers dropped bombs and torpedoes on the war ships, while the fighter planes attacked the US fighter planes on the ground so they could not take off and fight back. It was this that forced the United States to enter World War II.
Truman's potsdam declarationPresident Truman issued this ultimatum which stated that if Japan didn't surrender, the U.S. had to inflict "prompt and utter destruction". Japan didn't surrender since it looked like another threat. In August 6th, 1945, an atomic bomb dropped on Hiroshima killing more than 75,000 civilians. Japan didn't do anything. On August 9th 1945, a second atomic bomb dropped in Nagasaki, killing over 20,000 people.
End of the warJapan unconditionally surrendered in August 15, 1945. Allied civilians and military personnel celebrated V-J Day. On September 2, Japan signed the surrender documents. Isolated soldiers and personnel from Japan's far-flung forces through Asia and the Pacific refused to surrender for months and years afterwards. The war officially ended with the Treaty of San Francisco in 1952. Japan and the Soviet Union signed the Soviet–Japanese Joint Declaration of 1956.
(Time is 1945-1956)