After his recovery, he was named commanding general of the 337th Infantry Division from March 1942 until September 1942. Marcks was promoted to General der Artillerie and was named commanding general of the LXXXIV Corps, which he commanded during the Allied Normandy Invasion, and having had his 53rd birthday on D-Day, he was wounded in an Allied air attack on 12 June 1944 and died the same day.
After regaining his health, Marcks took command of the 337th Infantry Division from March to September 1942. He was promoted to General der Artillerie and led the LXXXIV Corps during the Allied invasion of Normandy on D-Day, where he turned 53 years old. Tragically, he was struck down by an Allied air raid on June 12, 1944.