The fourth day of Unternehmen Wacht am Rhein marked a decisive turning point. Kampfgruppe Peiper achieved its furthest penetration—35 miles from the Meuse—but was decisively contained and isolated after capturing Stoumont in a morning assault. On the Schnee Eifel, between 7,000 and 8,000 soldiers of the 106th Infantry Division surrendered, one of the largest mass surrenders in American military history. German High Command, recognising the failure of the 6. SS-Panzerarmee at Elsenborn, shifted the offensive’s focus southward to the 5. Panzerarmee.
The 2nd and 99th Infantry Divisions completed their withdrawal to Elsenborn Ridge, creating an impregnable defensive position with over 300 guns. The 1st Battalion, 117th Infantry recaptured Stavelot by noon, and engineers demolished the Amblève bridge with 1,000 pounds of TNT, isolating Kampfgruppe Peiper. At Verdun, Eisenhower convened an emergency meeting of senior commanders, where Patton pledged to attack with three divisions by 22 December.