In December of 1944, the Allied high command is convinced that German forces in Belgium are in a low state of readiness, and perhaps even about to withdraw. Only one officer on the front lines, intelligence specialist Lt. Col. Kiley (Henry Fonda), believes otherwise -- that the Germans are actually planning an attack. His opinion is rejected by his immediate superior (Dana Andrews) and his commanding general (Robert Ryan). Kiley spots several suspicious signs of German activity behind enemy lines on a reconnaissance flight, and he is at the front looking for evidence when the German counter-offensive starts. Taking advantage of Allied unpreparedness and a weather front that grounds all aircraft, their heavy tank units, supported by infantry, roll over the American forces, assaulting the lines at five different points in an attempt to ultimately divide the Allied forces in the west.