Cold War episode 4 - Berlin 1948-1949: In Berlin, the American, British and French sectors form a Western enclave in the Soviet zone of divided Germany. In June 1948, the Soviets blockade the city, but the Western allies successfully airlift in supplies. In August 1949, Soviet scientists explode an atomic bomb, establishing nuclear parity between the two superpowers. Opposed by the USSR, the United States emphasizes the need to rebuild the German economy.