August 13, 1961 The Berlin Wall began as a stretch of barbed wire and became a twentieth century symbol of a divided world. Here’s the story of its beginnings, in photos.

The Berlin Crisis was already underway in the summer of 1961. This escalation of the Cold War began with the Soviet Union demanding the withdrawal of British, French, and U.S. forces from Berlin. These Western troops, as well as their Soviet counterparts, had been in Germany as occupying forces since 1945. But Berlin’s status wasn’t settled: both soldiers and civilians had the right to move between the city’s western and eastern (Soviet) sectors. The Western allies rejected Moscow’s ultimatum. In response, the East German authorities closed the border between the city’s eastern and western sectors and began building the Berlin Wall — at first, it was primarily barbed wire entanglements and fences. After August 13, 1961, the city was divided in two for nearly 30 years. The wall became a barrier preventing Eastern Berliners from trying to flee to the West. And its fall in 1989 became the main symbol of the end of the Cold War and the collapse of communist regimes in Europe.