Until 1945, the state borders had been purely administrative boundaries with no formalities in crossing from one German state to another. This changed with the establishment of the occupation, although Germans were still permitted to travel from one zone to another and the borders were, in any case, not always clearly defined on the ground. The original Allied plan to govern Germany as a single unit through the Allied Control Council broke down in 1946–1947 due to growing Cold War tensions between the West and the Soviet Union, and was never fully implemented.