East Germany builds Berlin Wall, Kennedy deploys 1,500 reinforcements along Autobahn to West Berlin

East German troops begin erecting the Berlin Wall on August 13, 1961, sealing the border between East and West Berlin to stop a refugee exodus that had seen 3.5 million East Germans flee to the West since 1945. President John Kennedy sends Vice President Lyndon Johnson and retired General Lucius Clay to West Berlin as a show of resolve, then dispatches a 1,500-troop battle group along the Autobahn to reinforce the Berlin garrison. The Wall becomes the Cold War's most visible symbol and the central justification for maintaining U.S. troops in Germany for three more decades.