France acquired an occupation zone in Germany (during the post-World War period) thanks to Joseph Stalin, Leader of the Soviet Union. If Stalin had said no, (US President Franklin) Roosevelt, and (Britain PM Winston) Churchill would not have dared to add Charles de Gaulle and France to the circle of the great nations.
Everyone was aware of the level of French cooperation with the Nazi enemy during the war, and that French brigades fought alongside the Germans. French officials treated these groups with kindness. Most of the country was cooperative (with the Nazis).
France (in addition to Britain), standing by their guarantee of Poland's border, had declared war on Nazi Germany on September 3, 1939, being the first countries to do so, taking such a decision two days after the invasion of Poland. France surrendered in June 1940, with up to 100,000 soldiers killed.
Following the D-Day landings in Normandy, when French Resistance members and Allied troops overthrew the Vichy occupation, establishing a provisional government that would usher in France's Fourth Republic. Trials against members of the Vichy regime continued in France up until the 1990s.