At the close of WWII, the allies decided to split up the spoils of their victory and the Soviet Union took the land around Berlin. The city of Berlin was divided up by the four allies (the US, England, France, USSR), so that each had a sector of the city. It was agreed that there would be a road, a land bridge, from the west into west Berlin controlled by the US, England and France so that supplies could be trucked into West Berlin. However, the Soviets decided to block this access into the city so there was no way to supply the people in West Berlin. So the US started to fly in supplies and kept it up until the Soviets relented and reopened the road into West Berlin.