He began his assignment with the regiment in E Company as a platoon leader and was soon moved to the 2nd Battalion staff. He was transferred to the regimental staff before the D-Day invasions. Several days after drop, Matheson was wounded by German mortar fire while organizing a machine gun assault in French hedgerows on June 13, 1944. On June 15 he was awarded the Combat Infantryman Badge. After recovering from his injuries he parachuted into Holland and was later awarded the Bronze Service Arrowhead for participating in Operation Market Garden. Matheson was besieged with the rest of the 101st Airborne under the command of Maj. Gen. Anthony McAuliffe at Bastogne. During the Battle of the Bulge he was assigned as the S-4 of the 506th PIR and attempted without success to find small arms ammunition for his unit. Matheson served as the regimental logistics officer until March 1945, when he was moved to the position of Operations officer. Lt. Matheson helped lead the vanguard of the 101st toward Berchtesgarden and secured the surrenders of General Hans Speidel and Field Marshall Albert Kesslering.