How is postwar SEA impacted in USSR stayed out?

[Admiral Beez]

https://en.wikipedia.org/wiki/Soviet–Japanese_War

"At the Tehran Conference in November 1943, Joseph Stalin agreed that the Soviet Union would enter the war against Japan once Germany was defeated. At the Yalta Conference in February 1945, Stalin agreed to Alliedpleas to enter World War II in the Pacific Theater within three months of the end of the war in Europe. "

What if, instead at the Tehran Conference FDR and Churchill demand that the Soviet Union remain neutral and leave the war against Japan up to them? By Nov 1943, Rome has surrendered, and the Allied invasion of Italy is well underway, North Africa is free of Axis forces, and while we're still almost a year away from the final significant defeat of the IJN at the Battle of Leyte Gulf, Japan is clearly on the ropes. Four Essex and eight Independence class carriers and three Iowa class battleships have entered service and more of all three soon to commission. In Britain, the two Implacable class and sixteen Majestic/Colossus class are under construction, and the final two KGV class are now in service. It doesn't take a crystal ball to foresee the defeat or at least neutering and encirclement of Japan without USSR assistance. I expect some of FDR and Churchill's advisors were saying just that.

So, on condition of D-Day to relieve the USSR, the Soviets must remain neutral in the Far East. How does this impact the postwar world, such as in Korea and Vietnam?

 

[Dimlee]

Interesting question.
According to the Soviet and modern Russian "official" history, the USSR has generously agreed to assist Allies in their war against Japan. I always thought it was more complicated. If USSR stays neutral, future occupation zones will cover South Sakhalin and the Kuril Islands up to Kamchatka. Japanese control over the shipping routes changes to US control, not what the victorious USSR would like to have.
Most probably, Kremlin did have some plans with or without the invitation to join that war. How big those plans were we can only guess. There are tons of archive materials not unclassified yet.
Kim Il Sun was in the USSR since 1940, the 88th Brigade was formed in 1942, and Communists in Yunnan were bankrolled by Moscow directly since 1940.
If we look to South East, Ho Chi Minh lived and studied in Moscow and was a prominent Comintern agent in Asia before WWII. All Communist parties in SEA were linked to the Comintern.

 

[Thumpalumpacus]

My understanding is that with the Bomb still being uncertain of working, America welcomed the idea of Soviet help in an invasion of Japan at the time of Teheran; and Stalin understood that he needed to have some blood-equity in the Far East in order to lay any post-war claims.

Although we knew we'd have the IJN massively outnumbered by 1945, we Americans also had good reason to believe Japan would be a tough nut to crack, even before Tarawa.