At the outbreak of World War I, Garibaldi joined the French army at the head of the 4e régiment de marche du 1er étranger and later fought on the Italian front for Italy. In November 1915 his unit was the one that planted the Italian flag on the summit of Col di Lana. For this he received a promotion to colonel. He was promoted to brigadier-general in June 1918, retiring from the military one year later.