An Allied Japan reshapes the early Cold War

If Japan joined the Allies, how would Soviet behavior and the transition to the Cold War change?

The Soviet Union could emerge diplomatically isolated and face a stronger coalition in China, though the outcome depends on wartime alliances and postwar leadership.

If Moscow stayed outside an Anglo-American-Japanese wartime partnership, it could become the isolated power when the postwar settlement was written, accelerating Cold War alignment. Soviet support for Chinese communists might then meet coordinated British, American, and Japanese backing for the Nationalists. The result still depends on German strategy, American entry, and whether Attlee or Churchill leads Britain after the war.