During World War II, Sachs, along with disciple George L. Stout, was one of the people who developed plans to safeguard American works of art during the war, and one who set in motion the task force (later known as the Monuments Men) of American military officers who rescued European art and architecture during the war. In 1945, Sachs retired together from Fogg, while he remained on the teaching faculty of Harvard until 1948 when he was named a professor emeritus.