when was the berlin wall built

The Berlin Wall was built starting overnight on August 12 to 13, 1961. On the night of August 12 and into the early hours of August 13, East German troops and workers began erecting barriers, including barbed wire fencing, along the border separating East and West Berlin. Concrete blocks and more permanent structures followed soon after, with the first concrete elements being put in place by August 17, 1961. This construction was initiated by the government of the German Democratic Republic (East Germany) to prevent East Germans from fleeing to West Berlin. The date August 13, 1961, is commonly referred to as "Barbed Wire Sunday" in Germany to mark the beginning of the Wall's erection.