The document provides background information on the Berlin blockade and airlift. It explains that after World War 2, Berlin was divided among the Western allies and Soviet Union, with the western sectors becoming a "window into the West" that Stalin wanted to close. In 1948, Stalin blocked all access routes to West Berlin, cutting it off. The Western allies decided to fly in supplies and launch the Berlin airlift to provide for West Berliners rather than give into Stalin's demands or provoke war through invasion. Over the next 11 months, the airlift delivered 1.5 million tons of vital supplies through over 275,000 flights, keeping West Berlin alive.