As the Germans retreated from western Sicily (as a result of the Allied invasion, code-named Operation Husky), they halted and began setting up defences in the vicinity of the town of Troina along Highway 120, perched high on the hilltops.

By August 17, 1943, the 15th Panzergrenadier along with the 29th Infantry, the 1st Parachute and the Hermann Göring Divisions would escape across the Strait of Messina to the mainland and participate in the Italian Campaign.

Beginning on September 9, 1943, the Allied invasion of mainland Italy, (code-named Operation Avalanche), at Salerno and along the beaches to the southeast, found the 15th Panzergrenadiers among the principal defenders.

On December 7, 1943, two battalions of the 15th Panzergrenadier, commanded by Captain Helmut Meitzel, held strong defensive positions in the town of San Pietro Infine and on the vitally important and strategic Monte Lungo to the southwest.

Between January 20 and 22 1944, two battalions of the 15th Panzergrenadiers repulsed an ill-conceived assault by the US 36th Infantry Division, when the Allies were attempting to establish a bridgehead in the vicinity of the town of Sant' Angelo, to launch attacks on the Gustav Line near Monte Cassino.