From Wikipedia

Cold War

Episode Four

Berlin - 1948 - 1949

The Berlin Blockade
(24 June 1948 – 11 May 1949)
was one of the first major international crises of the Cold War and the first such crisis that resulted in casualties. During the multinational occupation of post-World War II Germany, the Soviet Union blocked the Western Allies' railway and road access to the sectors of Berlin under their control. Their aim was to force the western powers to allow the Soviet zone to start supplying Berlin with food and fuel, thereby giving the Soviets practical control over the entire city.