The Germans achieved a total surprise attack on the morning of 16 December 1944, due to a combination of Allied overconfidence, preoccupation with Allied offensive plans elsewhere and poor aerial reconnaissance due to bad weather. American forces were using this region primarily as a rest area for the U.S. First Army, and the lines were thinly held by fatigued troops and inexperienced replacement units. The Germans also took advantage of heavily overcast weather conditions that grounded the Allies' superior air forces for an extended period. American resistance on the northern shoulder of the offensive, around Elsenborn Ridge, and in the south, around Bastogne, blocked German access to key roads to the northwest and west which they had counted on for success. This congestion and terrain that favored the defenders, threw the German advance behind schedule and allowed the Allies to reinforce the thinly placed troops. The farthest west the offensive reached was the village of Foy-Nôtre-Dame, south east of Dinant, being stopped by the U.S. 2nd Armored Division on 24 December 1944.; ; . Improved weather conditions from around 24 December permitted air attacks on German forces and supply lines. On 26 December the lead element of Patton's U.S. Third Army reached Bastogne from the south ending the siege. Although the offensive was effectively broken by 27 December, when the trapped units of 2nd Panzer Division made two break-out attempts with only partial success, the battle continued for another month before the front line was effectively restored to its position prior to the attack.
The Germans achieved a total surprise attack on the morning of 16 December 1944, due to a combination of Allied overconfidence, preoccupation with Allied offensive plans elsewhere and poor aerial reconnaissance due to bad weather American forces were using this region primarily as a rest area for the U.S. First Army, and the lines were thinly held by fatigued troops and inexperienced replacement units. The Germans also took advantage of heavily overcast weather conditions that grounded the Allies' superior air forces for an extended period. American resistance on the northern shoulder of the offensive, around Elsenborn Ridge, and in the south, around Bastogne, blocked German access to key roads to the northwest and west which they had counted on for success. This congestion and terrain that favored the defenders, threw the German advance behind schedule and allowed the Allies to reinforce the thinly placed troops. The farthest west the offensive reached was the village of Foy-Nôtre-Dame, south east of Dinant, being stopped by the U.S. 2nd Armored Division on 24 December 1944.; ; . Improved weather conditions from around 24 December permitted air attacks on German forces and supply lines On 26 December the lead element of Patton's U.S. Third Army reached Bastogne from the south ending the siege. Although the offensive was effectively broken by 27 December, when the trapped units of 2nd Panzer Division made two break-out attempts with only partial success, the battle continued for another month before the front line was effectively restored to its position prior to the attack.