"As the war progressed and the Atlantic convoy routes and air-ferry routes from the United States to Britain became ever more important, control of Greenland and Iceland also become vital. The Danish government and king remained in Denmark under German occupation and were clearly not in a position to authorize occupation of Greenland or Iceland by forces of which the Germans would not approve.
The British had invaded Iceland in 1940 (before handing it over to us in 1941), and on April 9, 1941, a year after the German invasion of Denmark, FDR announced that the United States had concluded an agreement with the Danish envoy to the United States and with the support of the Greenlanders themselves to occupy Greenland and set up bases there.
Subsequently, thousands of US troops were sent to garrison Greenland, and airbases and a naval base were established.
And soon the war came even to Greenland. The Germans attempted to establish clandestine weather stations on the eastern side of Greenland in order to support their sea and air operations. And it was the job of US forces working with the Northeast Greenland Sledge Patrol to stop them. Greenland’s army consisted of only a few people and was the smallest in the Second World War. Nevertheless, this tiny war was a real one with important implications for the wider war, and people did die. One corporal in the Sledge Patrol was killed fighting in Greenland.
Sabine Island saw a number of incidents in this distant front of World War II. For instance, in spring 1943, a German post there was detected but then withdrawn before it could be attacked. Later, another German station was detected on the island, and this time, it was attacked by USAAF bombers based in Iceland, and then the Coast Guard went in."