WWII was a very hard fought battle. The pacific war in the 1940(s) was a hard fought battle. Casualties on both sides were high. The weapon at hand, the atomic bomb was on the U.S. side. Losing so many lives was what brought the U.S. to want to end the war. It was on August 6th 1945 that the U.S. would drop the atomic bomb over Hiroshima, Japan and force the Japan into a immediate, unconditional surrender. However, the Japanese debated over what to do. In the meantime, the U.S. dropped a second atomic bomb 3 days later over the city of Nagasaki Japan.
On August 14, 1945, Japanese Emperor Hirohito cabled the U.S. to surrender, and agreed to the terms of the Potsdam Declaration.
On August 15, 1945, news of the surrender was announced to the world. World War II was finally over. Hostilities ended. On September 2, 1945, the Japanese formally surrendered aboard the U.S. battleship USS Missouri in Tokyo Bay. President Truman declared this to be V-J Day.