Blitzkrieg – Lightning Warfare
On 1 September 1939 the German armed forces invaded Poland. Great Britain and France, allied with Poland, then declared war on the German Reich, but did not begin with fighting in the west. Thus the German Wehrmacht, which had almost completely moved in to the Eastern Front, could easily subjugate Poland within a few weeks. The boundaries of Germany were shifted to the east whilst Stalin, as Hitler's ally, annexed territories in eastern Poland. The «General Government of Poland» under German rule was then established in the remainder of Poland.
In the spring of 1940 German troops landed in Norway and marched into Denmark. The West Offensive began on 10 May, during which the Netherlands, Belgium and parts of France were occupied. Thus Germany controlled the entire Atlantic coast in the west, from northern Norway to the Bay of Biscay.