Greenland occupies a remarkable position in modern military history. Although it is geographically remote and covered largely by an enormous ice sheet, its location between North America and Europe has made it strategically important for more than a century. During the Second World War, the United States established a military presence there to prevent the island from being used by Germany and to support the defence of the North Atlantic. During the Cold War, Greenland became even more important as a base for air defence, nuclear deterrence, missile warning and Arctic surveillance.
The foundation for the postwar American military presence was the 1951 Defense of Greenland Agreement, signed by Denmark and the United States in Copenhagen on April 27, 1951. The agreement was negotiated within the framework of NATO and replaced the wartime 1941 agreement between the two countries. It remains the basic legal foundation for the American military presence in Greenland, although it has subsequently been modified.
Why Was Greenland Strategically Important?
Greenland's importance comes primarily from geography.
It lies between North America and Europe, astride the northern Atlantic routes. Aircraft and ships moving between North America and Europe could make use of Greenland, while its position also made it useful for weather observation, communications, air operations and the defence of the approaches to North America.
During the Second World War, the United States increasingly viewed Greenland as part of the defence system of the Western Hemisphere. The fall of Denmark to Germany in April 1940 created a particular problem. Denmark controlled Greenland, but the Danish government was no longer in a position to effectively defend its distant territory.
In April 1941, the United States and the Danish representative in Washington concluded the Agreement Relating to the Defense of Greenland. The agreement explicitly recognized Danish sovereignty while giving the United States extensive rights to construct and operate defence facilities. American officials described Greenland as a potential staging area between North America and Europe.
American forces subsequently established a network of airfields, weather stations, radio facilities and other installations. These facilities became part of the enormous logistical system connecting North America with the European and Arctic theatres.
The strategic importance of these facilities did not disappear with the defeat of Germany and Japan. The emerging Cold War actually made Greenland more important.
The 1951 Agreement
By 1951, the international situation had changed dramatically.
The Second World War was over, NATO had been created in 1949, and the Soviet Union had developed an atomic bomb. The United States therefore wanted long-term military access to Greenland.
The 1951 agreement was signed by Denmark and the United States pursuant to the North Atlantic Treaty. It was explicitly intended to serve NATO's collective defence. The agreement entered into force on June 8, 1951, following approval by the Danish parliament.
Importantly, this was not an agreement transferring Greenland to the United States. Danish sovereignty remained explicitly intact.
Instead, it created a framework under which the United States could establish and operate military facilities in Greenland.
Defense areas
The central concept was the creation of designated "defense areas."
The United States and Denmark would agree, based upon NATO defence plans, which areas were necessary for the defence of Greenland and the wider North Atlantic Treaty area.
Where the United States was given responsibility for operating a defence area, it received extensive authority to:
- develop the area for military purposes;
- construct and operate military installations;
- establish meteorological and communications facilities;
- store supplies;
- station American military personnel;
- provide housing and services for those personnel;
- protect the installation;
- operate postal facilities and commissaries;
- control aircraft and ship movements within the defence area; and
- improve harbours, channels and anchorages.
The agreement nevertheless stated that these arrangements were without prejudice to Danish sovereignty over the territory.
This distinction is important. The United States obtained extensive military rights, but it did not acquire sovereignty over the territory.
Access Across Greenland
The agreement also gave American military forces significant freedom of movement.
U.S. military ships, aircraft and vehicles were given rights of access between defence areas. American aircraft could fly over and land in Greenland, subject to arrangements agreed with Denmark.
Other NATO countries could also use the defence areas when required for NATO operations. Thus, the agreement was not simply a bilateral American-Danish arrangement. It was intended to provide military infrastructure for the collective defence of the North Atlantic alliance.
Denmark also agreed to provide, where practicable, weather and communications services and geographical information, including surveys and aerial photography useful to military operations.
What About American Jurisdiction?
The agreement gave the United States considerable jurisdiction within defence areas under American responsibility.
The United States could exercise exclusive jurisdiction over those areas with respect to American military and civilian personnel and certain other persons, although Danish citizens were specifically excluded from this provision and the agreement allowed the United States to turn offenders over to Danish authorities for trial.
The arrangement also gave American military and civilian personnel exemptions from various Danish taxes and duties, while American military supplies could enter Greenland without customs duties and similar charges.
These provisions were later affected by NATO's Status of Forces Agreement and subsequent arrangements.
Grønnedal
One interesting feature of the 1951 agreement was its treatment of Grønnedal, the important naval and communications facility in southern Greenland.
The United States had established the facility during the Second World War. Under the 1951 agreement, its operation was to be transferred to Denmark as soon as practicable.
The arrangement nevertheless preserved American and NATO access to the facility. American ships, aircraft and armed forces would retain access for the defence of Greenland and the North Atlantic. Denmark also assumed responsibility for the meteorological service and maintenance of the American buildings and equipment remaining there.
This illustrates an important characteristic of the agreement: not every American wartime installation was intended to remain an American base. The agreement created a framework for both American and Danish use of Greenland's military infrastructure.
The Agreement and Greenland's Population
One particularly striking aspect of the original agreement is its language concerning the Greenlandic population.
The United States agreed to respect Greenland's laws, regulations and customs concerning the local population. The original agreement also called for efforts to avoid contact between American personnel and the local population when Danish authorities considered such contact undesirable for military purposes.
This reflected the colonial circumstances of 1951. Greenland was still formally administered by Denmark and had not yet achieved the political status it possesses today.
The provision also became increasingly problematic as Greenland's political status evolved. In 1986, the restriction on contact between American personnel and the local population was revoked. The 2004 supplementary agreement formally recognized that change and introduced mechanisms for greater consultation with Greenlandic authorities.
The U.S. Military in Greenland During the Second World War
The 1951 agreement makes much more sense when viewed against the background of the American wartime presence.
The 1941 agreement allowed the United States to establish defence facilities while explicitly recognizing Danish sovereignty. American planners saw Greenland as valuable for protecting the Western Hemisphere and as a staging point for aircraft crossing the Atlantic.
By 1941, the United States already had forces in Greenland, and American officials were developing airfields there. One wartime planning document described Greenland's intended role as essentially a staging area between the United States and Europe.
The United States constructed and operated a network of facilities often identified by "Bluie" designations. These included airfields, weather stations, radio stations and other installations.
Some were permanent or semi-permanent; others existed primarily to support wartime operations.
The American presence also had an important logistical purpose. Greenland helped make it possible to move aircraft and personnel between North America and Europe through the North Atlantic.
For more on the Second World War, check out this podcast.
The Cold War Changes Everything
The end of the Second World War did not make Greenland less important.
It made Greenland important for a different reason.
The United States and its NATO allies now faced the Soviet Union. The development of long-range bombers and eventually intercontinental ballistic missiles made the Arctic an important potential avenue of attack.
American strategic planners consequently wanted to retain military rights in Greenland.
A 1949 U.S. government assessment described Greenland as strategically important to the defence of North America and emphasized the need to retain existing facilities and obtain additional military rights there.
The 1951 agreement provided the long-term legal framework for doing exactly that.
Thule Air Base
The most important result was the development of Thule Air Base in northwestern Greenland.
The base was constructed under Operation Blue Jay between 1951 and 1953. Its location was particularly valuable because it was much farther north than the wartime facilities and therefore ideally positioned for Arctic air defence and early warning.
Thule eventually became the centrepiece of the American military presence in Greenland.
During the Cold War, it supported:
- air defence;
- long-range radar;
- satellite tracking;
- communications;
- Arctic operations;
- missile warning; and
- strategic surveillance.
The installation became particularly important after the construction of the Ballistic Missile Early Warning System (BMEWS) site beginning in 1961. Its radar could detect incoming ballistic missiles approaching North America over the Arctic.
In 2023, Thule Air Base was renamed Pituffik Space Base, reflecting the facility's modern role in space operations and missile warning.
Camp Century and Project Iceworm
American military activity in Greenland went beyond conventional air bases.
In 1959, the U.S. Army established Camp Century, an extraordinary installation constructed beneath the Greenland ice sheet.
The facility consisted of tunnels and trenches dug into the ice and included laboratories, living quarters, storage areas and a nuclear reactor for electrical power. The Army used it for Arctic engineering and scientific research.
Camp Century is also famous because it was associated with Project Iceworm, a secret proposal to construct a network of underground facilities capable of deploying nuclear missiles beneath the Greenland ice sheet.
The project was eventually abandoned because movement of the ice made the proposed system impractical. Camp Century itself was abandoned in 1967.
The story demonstrates how Greenland had become part of the nuclear confrontation between the United States and Soviet Union.
The 1968 Thule Accident
The nuclear dimension of the American presence produced one of the most serious diplomatic crises in the history of U.S.-Danish relations.
On January 21, 1968, a U.S. B-52 bomber carrying nuclear weapons crashed near Thule.
The accident led to major Danish concern about nuclear weapons and nuclear-armed aircraft in Greenland. The 1951 agreement had not explicitly resolved every question concerning nuclear storage and overflights.
Following negotiations, the United States and Denmark reached an understanding in 1968 under which the United States agreed that it would not store nuclear weapons in Greenland or conduct nuclear-weapons overflights without Danish consent.
The episode demonstrated that the military relationship created by the 1951 agreement could produce difficult questions concerning Danish sovereignty and Greenlandic interests.
The Reduction of American Bases
The American military presence in Greenland has changed considerably since the Cold War.
At the height of the Cold War, the United States operated a much larger collection of facilities than it does today. By the late twentieth century, many had been closed as technology changed and the strategic environment evolved.
The 2004 agreement between the United States, Denmark and Greenland recognized this development. It stated explicitly that Thule Air Base was the only remaining U.S. defense area in Greenland. It also established greater mechanisms for cooperation with Greenland's Home Rule Government and consultation concerning significant changes in American military operations.
The same agreement noted that Greenland's political status had changed substantially since 1951, including the development of Greenlandic Home Rule.
Greenland Today
Today, the American military presence is concentrated primarily at Pituffik Space Base, the former Thule Air Base.
Its modern mission is considerably different from the enormous network of installations maintained during the early Cold War. The United States Space Force describes the installation as the Department of Defense's northernmost installation and identifies its missions as including force projection, space superiority, scientific research, missile warning and defence-related activities.
The base's missile-warning mission remains particularly significant. The original BMEWS installation established in 1961 evolved into the modern upgraded phased-array radar system.
Thus, the basic strategic logic has survived even though the technology has changed: Greenland provides an exceptionally important position for monitoring the Arctic approaches to North America and for supporting North American and NATO defence.
A Timeline of the U.S. Military Presence in Greenland
| Year | Event |
|---|---|
| 1941 | U.S.-Danish Defense of Greenland Agreement establishes American military rights. |
| 1941–45 | United States develops airfields, weather stations, communications facilities and other installations during WWII. |
| 1945 | Germany's defeat does not immediately end American interest in Greenland. |
| 1949 | NATO is created; Greenland becomes increasingly important to North Atlantic defence planning. |
| 1951 | New U.S.-Danish Defense Agreement signed, replacing the 1941 agreement. |
| 1951–53 | Operation Blue Jay constructs the modern Thule Air Base. |
| 1959 | U.S. Army establishes Camp Century beneath the Greenland ice sheet. |
| 1961 | Ballistic Missile Early Warning System begins development at Thule. |
| 1967 | Camp Century abandoned. |
| 1968 | B-52 carrying nuclear weapons crashes near Thule; subsequent negotiations address nuclear weapons and overflights. |
| 1986 | Restrictions on contact between U.S. personnel and the local population are revoked. |
| 2004 | New agreement brings Denmark and Greenland more directly into consultation concerning the American presence; Thule is identified as the only U.S. defence area. |
| 2023 | Thule Air Base renamed Pituffik Space Base. |
| Today | Pituffik remains a major American Arctic space and missile-warning installation. |
The Historical Significance of the 1951 Agreement
The 1951 Defense of Greenland Agreement is significant because it transformed what had begun as a wartime emergency arrangement into a long-term component of NATO's Arctic defence system.
The United States did not acquire Greenland. Danish sovereignty remained intact. Instead, Denmark granted the United States extensive rights to establish and operate military facilities in support of Greenland's and NATO's defence.
That distinction became increasingly important as Greenland's political status evolved.
The agreement also demonstrates how dramatically the strategic importance of the Arctic changed during the twentieth century. In 1941, Greenland was primarily important as a staging point and weather and communications centre for the North Atlantic war. By the 1950s and 1960s, it had become part of the American system for defending North America against Soviet bombers and missiles.
Today, the mission has evolved again toward space surveillance, missile warning and Arctic security.
In that sense, the history of the American military presence in Greenland can be seen as three overlapping eras: the Second World War's North Atlantic bridge, the Cold War's Arctic shield, and the modern system of Arctic and space defence. The 1951 agreement provided the legal foundation that allowed the transition from the first era into the second and, through subsequent modifications, into the third.
