Before dawn on 16 December 1944, German forces rolled through the frozen Ardennes in their last major offensive in the west, thus starting the Battle of the Bulge, which would become the U.S. Army's bloodiest engagement of World War II. Catching the Allies by surprise, the Germans made early gains, demolished the inexperienced U.S. 106th Infantry Division, and fought hard, but American counterattacks - and tenacious resistance in towns like Bastogne - combined with mounting German casualties and fuel shortages to force the German Army into a retreat from which it never recovered.