From: Japan Subdued: The Atomic Bomb and the End of the War in the Pacific by Herbert Feis, pp. 13-14.
Quote:
Marshall in his exposition at the White House Conference of June 18th had stated that our aim should be to have the Russians and Chinese "clean up" the situation on the mainland of Asia; to get the Russians to deal with the the Japanese forces in Manchuria; and those in Korea also, if necessary. He thought the the Russian entry might so affect the already hopeless Japanese that it might be the decisve action in causing them to surrender "...at that time or shortly thereafter if we land in Japan."[12] He then quoted MacArthur as observing, "The hazard and loss [of the landing on Kyushu] will be greatly lessened if an attack is launched from Siberia sufficiently ahead of our target date to commit the enemy to major combat..."
[12] Freeman memo of talk with MacArthur in February 1945. See "
The Entry of the Soviet Union into the War Against Japan: Military Plans, 1941-1945," cited in footnote 3.
Posted elsewhere, but I thought the readers here would find it interesting.