 Rorimer's career at the Met was interrupted by the United States' entry into World War II, and he signed up as an infantryman in the United States Army in 1943.He was soon appointed to a job more suited to his specialized skills, as an officer of the Monuments, Fine Arts and Archives Section (MFAA) in Normandy and Paris, and, later, in Germany.While in Paris, Rorimer had an auspicious encounter with Rose Valland, an art historian and employee of the Galerie Nationale du Jeu de Paume.