The Soviets plowed into Machuria and subsequently Northern Korea towards the end of WWII, occupying both until eventually giving Korea to Kim-il-Sung and Manchuria to Mao.
But what if the deal was different?
What if Stalin felt the American presence in South Korea was a more immediate threat to Soviet policy in the region and saught to further empower Kim, slicing off a part of lower Manchuria and redrawing the borders of North Korea to add everying from the Yalu River up to Shenyang and Harbin.
The rest is then given to Mao as per OTL.
What are the effects on both the Chinese Civil War and later Korean War.