Obviamente, este filme é A Batalha do Bulge (1965)
O incidente em questão aqui é o Massacre de Malmady
Schumacher later takes control of a vital intersection of three roads connecting Ambleve, Malmedy and the Siegfried Line. He sabotages the road signs, and the rear echelon of Wolenski's troops take the wrong road to Malmedy; almost the entire unit is captured and massacred. Lt. Weaver manages to escape, but Duquesne is killed. US soldiers become suspicious when they witness Schumacher's "military police" lay explosives incorrectly on the Our bridge, and his masquerade is revealed, though too late to stop Hessler.
Para mais informações, o verdadeiro pano de fundo do massacre é aqui