The Battle of the Bulge was a major German offensive and Allied counter-offensive lasting from 16 December 1944 through 25 January 1945. The Germans launched an assault of 13 divisions, 8 infantry and 5 armored, with about 200,000 men and over 340 tanks and 1,600 artillery pieces. The Allied forces, with just 4 infantry divisions and 1 armored division, about 83,000 men and 242 medium tanks, were taken by surprise. Ultimately, about 610,000 American men were involved in the battle, with 19,000 of them killed and 89,000 injured. The U.S. forces in the path of the German advance suffered the highest casualty rate for any U.S. operation of the entire war.
The Germans called it Unternehmen Wacht am Rhein or Operation Watch on the Rhine. To the French, it was the Bataille des Ardennes or the Battle of the Ardennes. The Allied forces referred to it as the Ardennes Counteroffensive.
The rapid German advance led to a pronounced westward bulge in the roughly north-south line of advance of the Allies. Newspapers began referring to it as the Battle of the Bulge in the stories accompanied by maps showing that bulge, and it became the most common name for the initial advance and Allied counteradvance.
The Allies had pushed east from the early June landings in Normandy, moving across France and into Belgium. By early to mid December they had advanced through Belgium past Antwerp and Brussels and were approaching the German cities of Düsseldorf and Cologne on the lower Rhine. Below is the situation as it stood on 15 December, the day before the German advance started.
The German pushed to the west during the ten days 16-25 December 1944 in their Unternehmen Wacht am Rhein. The "Bulge" westward in the German line and the source of the common name for the battle is obvious here.
A detail shows how Bastogne was almost entirely surrounded and cut off:
The Allied forces pushed back to the east 26 December 1944 through 25 January 1945:
As Stephen Ambrose describes it, "The 101st Airborne still had a complaint. As the story of the Battle of the Bulge is told today, it is one of George Patton and his Third Army coming to the rescue of the encircled 101st, like the cavalry come to save the settlers in their wagon circle. No member of the 101st has ever agreed that the division needed to be rescued!"