Greenland placed under United States military protection after the German occupation of Denmark, formalized by the Defense of Greenland agreement of 9 April 1941. The US built the “Bluie” airbases and weather stations while nominal Danish sovereignty continued.
US wartime garrison drew down after 1945; Greenland reverted to ordinary Danish administration (bases later continued under the 1951 NATO defense agreement).
Scholarly history of Greenland including the Danish colonial period and its wartime dislocation.