1,381 kilometres (858 mi) long and ran from the Baltic Sea to Czechoslovakia. It was formally established on 1 July 1945 as the boundary between the Western and Soviet occupation zones of Germany. On the Eastern side, it was made one of the world's most heavily fortified frontiers, defined by a continuous line of high metal fences and walls, barbed wire, alarms, trenches, watchtowers, automatic booby-traps and minefields. The border was a physical manifestation of Winston Churchill's metaphor of an Iron Curtain separating the Soviet and