The city centre was partially damaged by US Air Force bombing in 1945 with some 1,800 people killed and many historic buildings destroyed. Nevertheless, most of the destroyed buildings were restored soon after the war because of their importance in German cultural history. The Allied ground advance into Germany reached Weimar in April 1945, and the city surrendered to the US 80th Infantry Division on 12 April 1945. The residents of Weimar were ordered to walk through Buchenwald, to see what had been happening so close to the city, as documented in Billy Wilder's film "Death Mills". The city ended up in the Soviet zone of occupation, so US troops were soon replaced by Soviet forces.