He was the leader of a combat patrol on 21 December 1944, near Grufflingen, Belgium, with the mission of driving German forces from dug-in positions in a heavily wooded area. As he advanced his light machine gun, a German Mark III tank emerged from the enemy position and was quickly immobilized by fire from American light tanks supporting the patrol. Two of the enemy tankmen attempted to abandon their vehicle but were killed by Cpl. Thorne's shots before they could jump to the ground. To complete the destruction of the tank and its crew, Cpl. Thorne left his covered position and crept forward alone through intense machine-gun fire until close enough to toss two grenades into the tank's open turret, killing two more Germans. He returned across the same fire-beaten zone as heavy mortar fire began falling in the area, seized his machine gun, and, without help, dragged it to the knocked-out tank and set it up on the vehicle's rear deck. He fired short rapid bursts into the enemy positions from his advantageous but exposed location, killing or wounding eight. Two enemy machine-gun crews abandoned their positions and retreated in confusion. His gun jammed; but rather than leave his self-chosen post he attempted to clear the stoppage; enemy small-arms fire, concentrated on the tank, killed him instantly. Cpl. Thorne, displaying heroic initiative and intrepid fighting qualities, inflicted costly casualties on the enemy and insured the success of his patrol's mission by the sacrifice of his life.