On September 1, 1939, German troops invaded Poland. Britain and France declared war on Germany two days later. By the end of the month, Hitler's armies had overrun western Poland. Soviet armies occupied eastern Poland, and the two countries subsequently formally divided Poland between them. In April 1940, German forces conquered Denmark and Norway, and in May they struck at the Netherlands, Belgium, Luxembourg, and France. French and British troops offered ineffective resistance against the lightning-like strikes, or blitzkrieg, of German tanks and airplanes. A large part of the French army surrendered, and some 300,000 British and French soldiers were trapped at Dunkirk on the coast of northern France. However, because Hitler, for a combination of political and military reasons, had halted the advance of his armored divisions, the British were able to rescue the men at Dunkirk. France, however, surrendered in June.
For Hitler the war in the west was a sideshow, a prelude to the building of an empire in eastern Europe and the Soviet Union.
Hitler had hoped that Britain would stay out of the war. In his vision of the near future, he foresaw the two countries sharing the world between them--Britain would keep its overseas empire, and Germany would construct a new one to its east. When approached with the suggestion of a separate peace, British prime minister Winston Churchill rejected the offer and rallied his people to fight on. The Third Reich experienced its first military defeat in the Battle of Britain, in which the Royal Air Force, during the summer and fall of 1940, prevented the German air force from gaining the air superiority necessary for an invasion of Britain. Consequently, Hitler postponed the invasion.
Hitler concluded by June 1941 that Britain's continuing resistance was not a serious impediment to his main geopolitical...