the Arctic 1940: Invasion of Denmark and Norway
Germany had agreed to a partition of Eastern Europe with the Soviet Union, giving the Soviets leeway to attack Finland in late 1939. While the Allies were contemplating how to respond to this, Germany launched a lightning invasion of Denmark and Norway. The Allies, who had been preparing to intervene in Norway themselves, were caught by surprise.
3 Oct 1939 Declaration of Panama▲
The United States and the other neutral nations of North and South America signed the Declaration of Panama, setting up the Pan-American Security Zone. The signatories agreed not to tolerate belligerent acts within the zone, which extended from the US-Canada border to encompass the Americas to the south up to 1,000 nautical miles from the shore. The act mostly benefited the Allies as it restricted German U-boat activity in much of the western Atlantic.
30 Nov 1939–13 Mar 1940 Winter War▲
The Soviet Union invaded Finland with some 450,000 men, without declaring war and in violation of three non-aggression pacts. Despite numerical superiority, the Soviets suffered repeated setbacks until reinforcements allowed them to break through in January 1940. At the Moscow Peace Treaty, the Finns agreed to cede significant territory along the border of the two states, including the Karelian Isthmus.
9 Apr 1940 Invasion of Denmark▲
At 04:15 on 9 April 1940 German forces crossed the border into Denmark, while the Kriegsmarine landed troops at Lillebælt. Five minutes later, the 2,430 ton minelayer Hansestadt Danzig entered Copenhagen harbor with a small escort, landing a battalion of German Infantry at 05:18. While other amphibious and airborne landings took place across the country, the battalion quickly captured the Danish Army HQ and royal palace, prompting the Danish government to capitulate at 06:00 in exchange for retaining political independence in domestic matters.
9 Apr–10 Jun 1940 Norwegian Campaign▲
As part of Operation Weserübung—the invasion of Denmark and Norway—German forces landed along the coast of the Kingdom of Norway on 9 April 1940, capturing the towns of Oslo, Bergen, Trondheim, and Narvik on that same day. The operation was complicated by the arrival of the British in the north and continued Norwegian resistance in the interior, but by 1 June the Allies agreed the situation was hopeless. The Norwegian government evacuated on 7 June, with last resistance ending on 10 June.
10 Apr 1940 US warning on Greenland▲
Following the German occupation of Denmark, the United States affirmed that the Danish colony of Greenland was part of the Americas and thus subject to the Monroe Doctrine. In doing so, it rejected both the extension of German rule to the island and the possibility of British or Canadian intervention there.
10 Apr 1940 Icelandic self-rule▲
Following the German occupation of Denmark, the Icelandic Parliament declared Danish King Christian X unable to perform his constitutional duties and assigned them to the government of Iceland. Iceland opened a legation in New York city and declared itself neutral.