The Berlin Crisis of 1961 occurred between 4 June – 9 November 1961, and was the last major European politico-military incident of the Cold War about the occupational status of the German capital city, Berlin, and of post–World War II Germany. The Berlin Crisis started when the USSR issued an ultimatum demanding the withdrawal of all armed forces from Berlin, including the Western armed forces in West Berlin. The crisis culminated in the city's de facto partition with the East German erection of the Berlin Wall.