I think you'll find though that the claim "that the Russian campaign in Manchuria was the reason that the Japanese surrendered" is a little myopic.
Why did Truman order hostilities to be resumed?
Why did the USAAF want a 3rd bomb dropped as a wake up call on Tokyo? Because the Japanese were stalling on negotiations. It would seem a 3rd bomb was being prepared, but not for Tokyo, more likely Sapporo.
Why did the USAAF launch a 'thousand plane raid' on Aug14/15th?
Not me but several historians have pointed out the swift Russian victories impacted more on the Japanese leadership and brought about the surrender.