On what date did the Allied occupation of Japan begin in 1945?

The Allied occupation of Japan began on 28 August 1945.

On that date, the first U.S. personnel flew into Atsugi airfield in Kanagawa Prefecture. They were followed by additional Allied personnel and by forces connected with the formal surrender ceremony. General Douglas MacArthur arrived in Tokyo on 30 August and began directing the occupation from Japan.

The occupation’s beginning is often confused with 15 August, when Emperor Hirohito announced Japan’s surrender, or 2 September, when the surrender document was signed. Those dates mark the public announcement and formal capitulation, respectively. The occupation began between them.

The occupation was administered primarily by the United States with support from other Allied powers. It continued until the Treaty of San Francisco took effect on 28 April 1952. MacArthur served as Supreme Commander for the Allied Powers until General Matthew Ridgway replaced him in 1951.