"The Allies had delivered Japan an ultimatum to surrender on 28 July 1945.
When this was ignored, the US dropped two atomic bombs on Hiroshima on 6 August and Nagasaki on 9 August, the day Soviet forces invaded Manchuria.
The Allies celebrated victory over Japan on 15 August 1945, although the Japanese administration under General Koiso Kuniaki did not officially surrender with a signed document until 2 September.
Both dates are known as VJ Day." -http://news.bbc.co.uk
God Bless America.