The United States first occupied Greenland in 1941 specifically to keep it out of Nazi Germany’s hands and protect vital North Atlantic shipping lanes. Denmark had been occupied by Germany in April 1940. The US-Danish bilateral defense agreement signed April 9, 1941 — with the Danish ambassador in Washington acting against the German-occupied Copenhagen government’s authority — gave the US the right to establish military bases in Greenland for the duration of the war.

WHY THE GEOGRAPHY HASN’T CHANGED  

More than two-thirds of Greenland’s territory lies within the Arctic Circle. Its geographic position:

▸  North Atlantic: Greenland controls the GIUK Gap — Greenland-Iceland-United Kingdom — the choke point through which Russian submarines must pass to reach the Atlantic Ocean

▸  Arctic: as Arctic ice recedes, Greenland’s position on emerging Arctic shipping routes and resource extraction areas becomes more strategically valuable

▸  North American defense: Greenland is the northern anchor of North American early warning systems; Thule Air Base (now Pituffik Space Base) houses radar systems critical to ballistic missile early warning

WHAT TODAY’S DEAL ACTUALLY UPDATES  

The 1941 baseline — a wartime occupation agreement with a Denmark that no longer formally existed — has been updated through multiple successive agreements over 85 years. Today’s deal is the most recent update: expanded security authority, expanded commercial access, in the same territory that has been central to US Arctic strategy since the same strategic logic that drove 1941 drives 2026. The geography doesn’t change. The agreements that govern it do.

The US has been militarily present in Greenland since 1941. The strategic logic is unchanged: it controls the North Atlantic approach to the continent. The ice is receding and opening new Arctic routes, making it more valuable in 2026 than in 1941. Today’s deal is the latest update to an 85-year strategic relationship. Trump threatened to use force to update it. Denmark refused the threat. They updated it anyway.

CONFIDENCE: HIGH

US occupied Greenland in 1941; Nazi Germany controlled North Atlantic shipping lanes, two-thirds of the Arctic Circle, the GIUK Gap, and Pituffik Space Base, according to historical documentation and confirmed reporting.

SOURCES

▸  Historical documentation — Greenland WWII strategic history September 19, 2026