The Allied Supreme War Council decides to intervene in Norway and Finland. This vague and indecisive policy relies on the cooperation of neutral Norway and Sweden. The main motivation is the Allied desire to deny Germany access to Swedish iron ore supplies, which pass through the ice-free port of Narvik in Norway.
Sea War, North Sea
The British destroyer Cossack violates Norway’s neutrality to rescue 299 British merchant seamen aboard the German transport Altmark. Germany accelerates its invasion preparations, believing that Britain is planning more military actions in Norway.
Plans for the invasion of Western Europe are revised. The main focus of the offensive is changed to the Ardennes region after a suggestion by General Erich von Manstein. The bulk of the German Army’s armored units are allocated to this radical plan.