USS Missouri (BB-63) in the context of "Mamoru Shigemitsu"

The surrender of the Empire of Japan in World War II was announced by Emperor Hirohito on 15 August and formally signed on 2 September 1945, ending the war. By the end of July 1945, the Imperial Japanese Navy (IJN) was incapable of conducting major operations and an Allied invasion of Japan was imminent. Together with the United Kingdom and China, the United States called for the unconditional surrender of Japan in the Potsdam Declaration on 26 July 1945—the alternative being "prompt and utter destruction". While publicly stating their intent to fight on to the bitter end, Japan's leaders (the Supreme Council for the Direction of the War, also known as the "Big Six") were privately making entreaties to the publicly neutral Soviet Union to mediate peace on terms more favorable to the Japanese. While maintaining a sufficient level of diplomatic engagement with the Japanese to give them the impression they might be willing to mediate, the Soviets were covertly preparing to attack Japanese forces in Manchuria and Korea (in addition to South Sakhalin and the Kuril Islands) in fulfillment of promises they had secretly made to the US and the UK at the Tehran and Yalta Conferences.

On 6 August 1945, at 8:15 am local time, the United States detonated an atomic bomb over the Japanese city of Hiroshima. Sixteen hours later, American president Harry S. Truman called again for Japan's surrender, warning them to "expect a rain of ruin from the air, the like of which has never been seen on this earth." Late on 8 August 1945, in accordance with the Yalta agreements, but in violation of the Soviet–Japanese Neutrality Pact, the Soviet Union declared war on Japan, and soon after midnight on 9 August 1945, the Soviet Union invaded the Japanese puppet state of Manchukuo. Hours later, the U.S. dropped a second atomic bomb on the Japanese city of Nagasaki.

The Japanese Instrument of Surrender was the printed agreement that formalized the surrender of Japan, marking the end of hostilities in World War II. It was signed by representatives from Japan and from the Allied nations: the United States, China, the United Kingdom (UK), the Soviet Union, Australia, Canada, France, the Netherlands, and New Zealand. The signing took place on the deck of USS Missouri in Tokyo Bay on 2 September 1945.

The date is sometimes known as Victory over Japan Day. However, that designation more frequently refers to the date of Emperor Hirohito's Gyokuon-hōsō (Imperial Rescript of Surrender), the radio broadcast announcement of the acceptance of the terms of the Potsdam Declaration at noon Japan Standard Time on 15 August.

World War II officially ended in Asia on September 2, 1945, at 3:24 with the surrender of Japan on the USS Missouri. 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 American occupation of Japan lasted from the end of the war until April 28, 1952, when the Treaty of San Francisco came into effect.

Surrender, in military terms, is the relinquishment of control over territory, combatants, fortifications, ships or armament to another power. A surrender may be accomplished peacefully or it may be the result of defeat in battle. A sovereign state may surrender following defeat in a war, usually by signing a peace treaty or capitulation agreement. A battlefield surrender, either by individuals or when ordered by officers, normally results in those surrendering becoming prisoners of war.

Toshikazu Kase (加瀬 俊一, Kase Toshikazu; January 12, 1903 – May 21, 2004) was a Japanese civil servant and career diplomat. During World War II he was a high-ranking Foreign Ministry official. Hideaki Kase (1936–2022) was his son and Yoko Ono is his niece.