The French Forces of the Interior (French: Forces françaises de l'Intérieur) were French resistance fighters in the later stages of World War II. Charles de Gaulle used it as a formal name for the resistance fighters. The change in designation of these groups to FFI occurred as France's status changed from that of an occupied nation to one of a nation being liberated by the Allied armies. As regions of France were liberated, the FFI were more formally organized into light infantry units and served as a valuable manpower addition to regular Free French forces. In this role, the FFI units manned less active areas of the front lines, allowing regular French army units to practice economy of force measures and mass their troops in decisive areas of the front. Finally, from October 1944 and wit