As a soldier in the French Army in World War I, Mare led the development of military camouflage, painting artillery using Cubism techniques to deceive the eye. He authored the book Cubism et Camouflage, 1914-1918.
Mare sketched and painted scenes based on his experiences in World War I. Some of his works include:
American Troops Marching Through the Arch of Triumph, 1930, and The Funeral of Marshall Foch, 1931.
As a painter and interior designer after the war, he combined his talents with the skills of architect Louis Sue and became a leader in the art deco movement of the early 20th century.