Germany War II in Europe. In response to Hitler's actions, two days later, on 3 September, after a British ultimatum to Germany to cease military operations was ignored, Britain and France declared war on Germany. In the spring of 1940, Germany conquered Denmark and Norway, the Netherlands, Belgium, Luxembourg, and France forcing the French government to sign an armistice after German troops occupied most of the country. The British repelled German air attacks in the Battle of Britain in the same year. In 1941, German troops invaded Yugoslavia, Greece and the Soviet Union. By 1942, Germany and other Axis powers controlled
France–Germany relations By the war's end, the French army occupied south-west Germany and a part of Austria. Marshal Petain, who ruled France under German supervision, 1940-44, adopted the ideology of National Revolution which was originally based on ideas which had been discussed for years. When the Franco-German reconciliation committee "Comité France-Allemagne" ("French-German Friendship Committee") founded in 1935 in Paris it was an important element for Germany to get closer to France. It adopted Pro-European, Pro-German, anti British, anti liberal political and economic views. Key members of the Committee became the key leaders of the French collaborators with Nazis after 1940. When Marshal