No agreement was reached and in August 1961, with Khrushchev's backing, East German leader Walter Ulbricht ordered the closing of the border and the construction of a wall around West Berlin.
The East German government also sought a way to stop its 'brain drain' as its population fled west through Berlin, made possible by the city's four-power status and the allowance of free travel. Kennedy at the Vienna summit, reissued an ultimatum which demanded the withdrawal of all armed forces from Berlin, including the Western armed forces in West Berlin. The Berlin Crisis began in June 1961 when Soviet Premier Nikita Khrushchev, meeting with US President John F. The crisis culminated in the city's de facto partition with the East German erection of the Berlin Wall. The Berlin Crisis of 1961 ( German: Berlin-Krise) was the last major European political and military incident of the Cold War concerning the status of the German capital city, Berlin, and of post–World War II Germany. Erection of the Berlin Wall on 12–13 August 1961.
