The shock of the A-Bombs seems to have been the determining factor. The Soviets crushed the Japanese in a massive defeat, but then they didn't seem phased by our crushing defeat of them either, so I'd say the Soviet invasion of Manchuria probably had little effect on the decision.
Something that might have contributed to the Japanese surrender in regards to the Manchuria offensive is; the Japanese relocated industries to this part of their area to protect them from the US Army Air Corps. Even though, the Japs must have had problems to get the equipment out from Manchuria due to the lack of means of transportation.
I'm not sure how heavily the Americans targets shipping from North China - Manchuria however I do know for the most part most of the shipments to Japan were ending up at the bottom of the sea due in large part to the successful American submarine campaign against Japan.
I'm not sure how heavily the Americans targets shipping from North China - Manchuria however I do know for the most part most of the shipments to Japan were ending up at the bottom of the sea due in large part to the successful American submarine campaign against Japan.
Between the "Hell's Bells" device that allowed subs to enter the Inland Sea & the B-29s air dropping mines.......Yes, the US submarines were very successful to cut the Japanese islands off so any merchant ships from Korea would have been a prime target. Even later when the US naval forces were pretty close to the home islands, the Japs couldn't get anything of significance out from Korean ports prior the USSR offensive.