A Soviet Hokkaido would break America's northern Pacific island barrier

How would a Soviet-held Hokkaido develop, and could there be a Japanese war alongside the Korean War?

It would give the Soviet Union a strategically valuable Japanese island, damage relations with the rest of Japan, and weaken the northern Pacific island barrier rather than create a simple second Korea.

Washington would have strong strategic reasons to reject a Soviet claim to Hokkaido. The island would connect with Vladivostok and open a gap in the chain used to contain Soviet naval power. Its smaller population and separation from the rest of Japan make a Korean-style land war less plausible. Any renewed conflict would depend more on blockade, amphibious operations, and the political loyalty created by leaving the emperor in the American-controlled part of Japan. The later conclusion favours direct Soviet annexation, using Sakhalin as an analogy, over a separate North Japanese state.