In June 1948, enraged over political and economic reforms that would give rise to West Germany, Joseph Stalin stopped all road and rail traffic coming into and out of the Allied sector of Berlin. He simultaneously cut off all electricity to the city, leaving only a 20-mile-wide sector of air corridors and one way to get supplies to Germany's capital city. The United States, using the only method it could, led Allies in mobilizing an unprecedented airlift of thousands of tons of supplies each day. At the same time, the Russian military threatened to strike down any aircraft caught flying outside of the corridor, putting allied pilots in peril if their navigation was faulty. The inspiring story of the Berlin Airlift gave the allies a badly needed boost, at the beginning of the Cold War.