The offensive commenced on 16 November 1944 with one of the heaviest Allied tactical bombings of the war. However, the Allied advance was unexpectedly slow, against heavy German resistance, especially in the Hürtgen Forest through which the main thrust of the offensive was carried out. By mid-December, the Allies finally reached the Rur and tried to capture its important dams, when the Germans launched their own offensive, dubbed "Wacht am Rhein". The ensuing Battle of the Bulge led to the immediate cessation of Allied offensive efforts into Germany until February 1945.