Nazi Germany invaded France in May 1940. Their unstoppable advance through the undefended Ardennes caused a crisis in the French government; the French Third Republic dissolved itself in July, and handed over absolute power to Marshal Philippe Pétain, an elderly hero of World War I. Pétain signed an armistice with Germany with the north and west of France under German military occupation. Pétain, charged with calling a Constitutional Authority, instead established an authoritarian government in the spa town of Vichy, in the southern "zone libre" ("free zone"). Though nominally independent, Vichy France became a collaborationist regime and was little more than a Nazi client state that actively participated in Jewish deportations.