The liberation of France in the Second World War was accomplished through diplomacy, politics and the combined military efforts of the Allied Powers, Free French forces in London and Africa, as well as the French Resistance. Nazi Germany invaded France in May 1940. Their rapid 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. Even before France surrendered on 22 June 1940, General Charles de Gaulle fled to London, from where he called on his fellow citizens to resist the Germans. The British recognized and funded Free French government in exile based in London. Efforts to liberate France began in the autumn of 1940 in France's colonial empire in Africa, still in the hands of the Vichy regime. General persuaded French Chad to support Free France, and by 1943 most other French colonies in Equatorial and North Africa had followed suit. announced formation of the Empire Defense Council in Brazzaville, which became the capital of Free France. In 1942 an Anglo-American invasion force landed in the French North African territories, completing Allied domination of the Mediterranean Sea, from which they invaded Italy. A French Expeditionary Corps of mostly colonial troops fought under the Allied command in Italy. Allied military efforts in north western Europe began in summer 1944 with two seaborne invasions of France. Operation Overlord in June 1944 landed two million men, including a French armoured division, through the beaches of Normandy, opening a Western front against Germany. Operation Dragoon in August launched a second offensive force, including French Army B, from the département of Algeria into southern France. City after city in France was liberated, and even Paris was liberated on 25 August 1944. As the liberation progressed, resistance groups were incorporated into the Allied strength. In September, under threat of the Allied advance Pétain and the remains of the Vichy regime fled into exile