The inexperienced troops of the division were lodged on the northern shoulder of the Ardennes Offensive on 16 December. Although cut up and surrounded in part, the 99th was one of the only divisions that did not yield to the German attack, and held their positions until reinforcements arrived. The lines were then moved back to form defensive positions east of Elsenborn Ridge on the 19th. Here it held firmly against violent enemy attacks. From 21 December 1944 to 30 January 1945, the unit was engaged in aggressive patrolling and reequipping. It attacked toward the Monschau Forest, 1 February, mopping up and patrolling until it was relieved for training and rehabilitation, 13 February.