He was pinned down with other members of his company during an attack against strong enemy positions in the vicinity of Untergriesheim, Germany. Heavy artillery, mortar, and machinegun fire made any move hazardous when he stood up, shouted to the company to follow, and ran forward in the wake of a supporting tank, firing his machine pistol. Inspired by his example, his comrades advanced in the face of savage enemy fire. When his weapon was struck by shrapnel and rendered useless, he climbed to the deck of a friendly tank, manned an exposed machinegun on the turret of the vehicle, and, while bullets rattled about him, fired at an enemy emplacement with such devastating accuracy that he killed or wounded at least 10 hostile soldiers and destroyed their machinegun. Maintaining his extremely dangerous post as the tank forged ahead, he blasted 3 more positions, destroyed another machinegun emplacement and silenced all resistance in his area, killing at least 3 and wounding an undetermined number of riflemen as they fled. His machinegun eventually jammed; so he secured a submachinegun from the tank crew to continue his attack on foot. When our armored forces exhausted their ammunition and the order to withdraw was given, he remained behind to help a seriously wounded comrade over several hundred yards of open terrain rocked by an intense enemy artillery and mortar barrage. By his intrepidity and inspiring courage Pfc. Colalillo gave tremendous impetus to his company's attack, killed or wounded 25 of the enemy in bitter fighting, and assisted a wounded soldier in reaching the American lines at great risk of his own life.