The Berlin Blockade was a period when the Soviet Union blocked all access into Berlin. Germany got split into 4 after WW2 ( British, French, USA and USSR). USA, France and Britain introduced Deutschmark. USSR then closed all water and land routes into Berlin. The only solution was to airlift food, medical supplies and fuel into Berlin through Hanover, Hamburg and Frankfurt. Cargo planes flown in 1 every 90 seconds and the Soviets disrupted them by putting weather balloons and planes in the way.