One of the more decisive decisions of the Occupation of Japan, that Japan would remain one state, was made early in the process by General MacArthur. The Soviets planned to occupy the northern island of Hokkaido and establish a puppet Soviet regime, identical to what was occurring in East Germany. If this had succeeded, Japan could have been divided into a Communist North Japan and a Democratic South Japan for the length of the Cold War. Appeasement of the Soviets was still very much in favor at the State Department, and it is possible that if the Soviets had simply begun landing in Hokkaido, that Washington may have capitulated on that point. After all, the Soviets were full members, with Great Britain, in the Allied commission to supervise and monitor the Supreme Commander in Tokyo. The Soviets also insisted upon a tri-partite division of Tokyo, similar to what was being done in Berlin. MacArthur would have none of it.
When Soviet Lieutenant General Kuzma Derevyanko, head of the Soviet military delegation in Japan, advised MacArthur that the Soviets planned to land in Hokkaido without his permission, MacArthur’s reaction was blunt: “I told him that if a single Soviet soldier entered Japan without my authority, I would at once throw the entire Soviet mission, including himself, into jail.” Derevyanko believed him, and more to the point so did Stalin. No Soviet landings occurred in Hokkaido. Japan would remain one country, to the vast relief and joy of the Japanese.