The Cold War Agreement That Opened Greenland to the US Military

When Denmark was occupied by Germany during World War II, the United States signed a pact with Denmark’s U.S. ambassador to protect Greenland—then a Danish colony—from Nazi invasion. After Germany was defeated, U.S. forces were prepared to leave Greenland when a new threat emerged: the Soviet Union.

In April 1949, after several Eastern European countries fell to Soviet-backed communist revolutions, 12 nations—including the U.S. and Denmark—formed the North Atlantic Treaty Organization (NATO) as a defensive alliance against Soviet aggression. Months later, the USSR successfully detonated its first nuclear bomb, raising the stakes of the Cold War even higher.

With the threat of Soviet bombers flying over the Arctic to strike targets in North America, Greenland became critical to U.S. and NATO defense strategies. Under NATO’s direction, the U.S. and Denmark met in 1951 to negotiate an updated agreement for the defense of Greenland.

“The treaty of 1951 was all about positioning the United States so we had the presence we needed in that emergent nuclear world,” says Barry Zellen, a senior fellow in Arctic security at the Institute of the North.

The 1951 Defense of Greenland agreement granted the U.S. the right to expand its military presence in Greenland far beyond World War II levels. The largest addition was the construction of Thule Air Base (now Pituffik Space Base) in Greenland’s frozen north, which was manned by more than 10,000 U.S. troops at the height of the Cold War.

Denmark declared its neutrality at the onset of World War II, but Germany still invaded in 1940 and placed Denmark under Nazi occupation. Since Greenland was a Danish colony, there was great concern in the United States that Germany would invade Greenland too, giving the Nazis a North American base of operations.

“If Britain fell, the Nazis were thinking about how they could expand beyond Europe,” says Zellen, author of Arctic Exceptionalism: Cooperation in a Contested World. “One of the plans was to get into Greenland, then extend beyond Greenland to grab Labrador and Newfoundland. All that [North American] territory was in play.”

With the Danish government under Nazi control, the Danish ambassador in Washington, Henrik Kauffmann, acted on his own and signed a 1941 defense agreement giving the United States broad authority to build airstrips and ports in Greenland and to station U.S. military personnel on the island.

Over the next four years, the U.S. built 13 Army bases and four Navy bases in Greenland manned by nearly 5,800 military personnel. By 1944, American troops constituted roughly 25 percent of Greenland’s population.

After World War II, Greenland took on a new strategic importance during the anxious early days of the Cold War. Once the Soviets got nuclear weapons in 1949, the U.S. and its NATO allies wanted a beefed-up military presence in the Arctic to detect Soviet bombers.

Denmark, still reeling economically from the war, was in no position to provide that level of military support in Greenland. In 1951, NATO directed the U.S. and Denmark to negotiate a treaty that would provide for the mutual defense of both Greenland and “the rest of the North Atlantic Treaty area.”

What NATO and Denmark didn’t know was that the U.S. had already secretly decided to build a massive U.S. air base at Thule in northern Greenland. The project, codenamed “Blue Jay,” was greenlit in December 1950 as the linchpin of a new U.S. nuclear defense strategy in the Arctic.

“The fear was that a Soviet plane with an atomic weapon strapped to its belly could zigzag its way across the high North Atlantic, pop over Eastern Canada and drop a nuke on New York,” Zellen says. “And so the U.S. wanted to have a presence in Greenland to conduct aerial surveillance of the horizon.”

When the U.S. met with Danish negotiators in 1951, the Americans presented a draft of the Greenland defense agreement that barely mentioned the Kingdom of Denmark at all. The U.S. negotiators were so focused on their unspoken goal of building the Thule base, that they overlooked Denmark’s rightful claims to sovereignty in Greenland.

In response, the Danish chief negotiator said that the Americans’ draft of the defense agreement gave the impression “that we have practically sold Greenland to the United States.” (Indigenous Greenlanders were not part of the 1951 negotiations.)

In reality, Denmark did not have much bargaining power in the negotiations over the future security of Greenland. NATO’s “mutual defense” orders were clear, and the U.S. was the only country with the military resources to provide defense for the island.

In the end, the U.S. got everything it needed from the 1951 Defense of Greenland agreement to build its secret air base at Thule. The U.S. could construct military installations, house troops and operate with near-total immunity in its “defense areas” within Greenland.

As minor concessions to Denmark, the 1951 agreement included language recognizing “the sovereignty of the Kingdom of Denmark” and “the natural right of the competent Danish authorities to free movement everywhere in Greenland.”

Zellen sees the 1951 Defense of Greenland agreement as part of a critical unified stance by the U.S. and its allies against a common Cold War enemy. “The Greenland treaty in 1951 was a natural adjunct to the formation of NATO in 1949,” he says.

Thule Air Base, constructed between 1951 and 1953, required 12,000 workers and shipments of 300,000 tons of cargo. At the peak of the Cold War, it housed 10,000 American troops. The base gave the U.S. a rapid-response capability to Soviet nuclear threats, since American bombers taking off from Thule could reach targets like Leningrad (now St. Petersburg) and Moscow in a matter of hours.

Although the U.S. greatly reduced its military presence in Greenland after the end of the Cold War, the 1951 defense agreement remains in effect. The pact was last amended in 2004 to recognize Greenland’s Home Rule government (established in 1979) but not to restrict U.S. military operations on the island.