Not entirely accurate.
If memory serves me right, the Soviet Union declared war on Japan before the end of hostilities in WWII.
August 6 - First atomic bomb dropped on Hiroshima.
August 8 - The Soviet Union declare war on Japan and invades Manchuria.
August 9 - Second atomic bomb dropped on Nagasaki.
August 14 - Japan agrees to unconditional surrender with the understanding that the emperor Hirohito will stay.
Frankly, I don't think the USSR was a great deal of help in the war. LOL