World War II officially ended in Asia on September 2, 1945, with the surrender of Japan on the . Before that, the United States dropped two atomic bombs on Japan, and the Soviet Union declared war on Japan, causing Emperor Hirohito to announce the acceptance of the Potsdam Declaration on August 15, 1945, which would eventually lead to the surrender ceremony on September 2.
After the ceremony, Japanese forces continued to surrender across the Pacific, with the last major surrender occurring on October 25, 1945, with the surrender of Japanese forces in Taiwan to Chiang Kai-shek. The Americans and British occupied Japan after the end of the war until April 28, 1952, when the Treaty of San Francisco came into effect.
Prelude
Soviet agreements to invade Japan
At the Tehran Conference, between November 28 and December 1, 1943, the Soviet Union agreed to invade Japan "after the defeat of Germany", but this would not be finalized until the Yalta Conference between February 4 and February 11, 1945, when the Soviet Union agreed to invade Japan within 2 or 3 months. On April 5, 1945, the Soviet Union denounced the Soviet–Japanese Neutrality Pact that had been signed on April 13, 1941, as now the Soviet Union had plans for war with Japan.
Surrender of Axis forces in Europe
Japan's biggest allies in Europe began to surrender in 1945, with the last Italian troops surrender in the "Rendition of Caserta" on April 29, 1945, and the Germans surrendering on May 8, 1945, leaving Japan as the last major Axis power standing.
The Potsdam Conference and Declaration
On July 17, 1945, the Potsdam Conference began. While mostly dealing with events in Europe after the Axis surrenders, the Allies also discussed the war against Japan, leading to the Potsdam Declaration being issued on July 26, 1945, calling for the unconditional surrender of Japan, and "prompt and utter destruction" if Japan failed to surrender. Yet, the ultimatum also claimed that Japan would not "be enslaved as a race or destroyed as a nation".
Japan's peace attempts and response to the Potsdam Declaration
Peace attempts
Before the Potsdam Declaration was issued, Japan had wanted to attempt peace with the Allies, with some early moves by the government apparent as early as the spring of 1944. By the time the Suzuki cabinet took office on April 7, 1945, it became clear that the government's unannounced aim was to secure peace. The repeated attempts to establish unofficial communication with the Allies included sending Prince Fumimaro Konoe to Moscow to try to get the Soviet Union to make the Americans stop the war. However, the Soviet Union did not want the Allies to have peace with Japan until they declared war on Japan.
Response to the Potsdam Declaration
When the Potsdam Declaration was issued, Japan's government followed a policy of mokusatsu, which can be roughly translated as "to withhold comment", most likely the closest to what the government meant. However, Japan's propaganda agencies, like Radio Tokyo and the Domei News Agency, broadcast that Japan was "ignoring" the Potsdam Declaration, another possible translation of mokusatsu, making it seem like Japan outright ignored the Potsdam Declaration, leading to the United States dropping nuclear weapons on Japan a few days later.
Final stages
Before the informal surrender of Japan
Atomic bombings of Hiroshima and Nagasaki
On August 6, 1945, a gun-type nuclear bomb, Little Boy, was dropped on Hiroshima from a special B-29 Superfortress named Enola Gay, flown by Col. Paul Tibbets. It was the first use of atomic weapons in combat. 70,000 were killed instantly; 30,000 more would die by the end of the year. Hiroshima was chosen as the target to demonstrate the destructiveness of the bomb.
After the bombing of Hiroshima, Harry Truman said that "We have spent two billion dollars on the greatest scientific gamble in history—and won." Japan still continued the war, though, despite some officials' attempts to make peace through the Soviets.
On August 9, 1945, a second, and more powerful plutonium implosion atomic bomb, Fat Man, was dropped on Nagasaki from a different Silverplate B-29 named Bockscar, flown by Major General Charles Sweeney. The original target was Kokura, but thick clouds covered the city, so the plane was flown to the secondary target, Nagasaki, instead. It killed 40,000 instantly, and another 30,000 would die by the end of the year.
The atomic bombings were one possible reason why Emperor Hirohito decided to surrender to the Allies.