In the east was the Soviet Union, with which Germany was still on good terms. The German invasion of Denmark was the fighting that followed the German army crossing the Danish border on 9 April 1940 by land, sea and air. This was due to the pact of nonaggression signed before the beginning of World War II. The German ground campaign against Denmark was the briefest on record in military history. An assault was not necessary, since, with control over Norway and Denmark, the Third Reich surrounded Sweden from the north, west and south.