The Unity of the Realm

Medieval origins: Faroe Islands and Greenland under the Norwegian Crown

The roots of the present Unity of the Realm reach back nearly a thousand years. The Faroe Islands, populated since around AD 500 and settled by Norse Vikings in the 9th century, became part of the Kingdom of Norway in 1035.^[5] Greenland — settled by Erik the Red and Norse colonists from Iceland in the late 10th century — became a subject territory of the Norwegian Crown in 1261. In the medieval period, Greenland was a bishopric with 22 churches and two convents, administered under the archdiocese of Nidaros.^[6]

The Kalmar Union (1397–1523): the North Atlantic under the Danish Crown

The decisive moment connecting the North Atlantic territories to Denmark came on 17 June 1397, when Erik of Pomerania was crowned king of Denmark, Norway, and Sweden in the cathedral of Kalmar, Sweden, establishing the Kalmar Union.^[7] The union had been engineered by Queen Margaret I of Denmark, who through her regency over Denmark and Norway had already brought the Faroe Islands and Greenland under her authority. The Kalmar Union joined under a single monarch the three kingdoms of Denmark, Norway, and Sweden together with Norway's overseas dependencies — Iceland, Greenland, the Faroe Islands, and the Northern Isles of Orkney and Shetland.^[8]

When Sweden finally broke from the union in 1523, the remaining Denmark–Norway twin kingdom retained full control of the North Atlantic dependencies. The Faroe Islands and Greenland would remain part of this joint Dano-Norwegian monarchy for nearly three more centuries.

The Treaty of Kiel (1814): the decisive break

The Napoleonic Wars permanently reshaped the realm. Denmark, allied with Napoleonic France, was forced to capitulate after Swedish-allied forces invaded Holstein and Schleswig. By the Treaty of Kiel, signed on 14 January 1814, Denmark ceded the Kingdom of Norway to the Swedish Crown. However, Greenland, Iceland, and the Faroe Islands were explicitly excepted from the cession and remained under Danish sovereignty.^[9] Article IV of the treaty stated that the Danish king "irrevocably and forever" renounced claims to Norway proper, while the three North Atlantic territories were categorically excluded from the transfer.^[10]

The reasons for this exception remain debated by historians. Britain is believed to have had a strategic interest in preventing Sweden — and thereby Russia's ally — from gaining dominance over the North Atlantic.^[11] The result was that Denmark retained what had been Norway's great medieval colonial holdings, establishing the geographic basis for today's Unity of the Realm.

Norwegian sovereignty over parts of Greenland was challenged again between 1931 and 1933, when Norway occupied parts of East Greenland and brought the dispute before the Permanent Court of International Justice in The Hague. On 5 April 1933, the court ruled in Denmark's favour, confirming Danish sovereignty over the whole island on the basis of the Treaty of Kiel and subsequent treaties.^[10]

The Constitution of 1953: integration and decolonisation

The constitutional framework underpinning the modern Unity of the Realm was established by the Danish Constitution of 1953, whose opening paragraph stated that it "shall apply to all parts of the Kingdom of Denmark", explicitly binding Denmark, the Faroe Islands, and Greenland into a single constitutional order.^[2] For Greenland, which Denmark had governed as a colony since missionary Hans Egede arrived in 1721, the 1953 constitution represented formal decolonisation through integration: Greenland became an ordinary Danish county, and the UN General Assembly subsequently accepted that Denmark's obligations under Chapter XI of the UN Charter regarding non-self-governing territories had been fulfilled.^[12] The 1953 constitution also guaranteed both the Faroe Islands and Greenland two elected members each in the Folketing.^[2]

The Faroe Islands, by contrast, had never been considered a colony. They had been formally an equal part of Denmark since the first democratic constitution of 1849, and had already obtained their own home rule arrangement in 1948.^[13]

The Faroe Islands

The Faroe Islands obtained home rule under the Faroe Islands Home Rule Act (Act no. 137 of 23 March 1948), in recognition of the islands' special historical, national, and geographical position within the Kingdom.^[14] The act established the Faroe Islands as a self-governing community within Denmark, transferring a range of administrative and legislative powers to Faroese authorities, and replaced the governor (Amtmand) with a High Commissioner (Rigsombudsmand) as the state's senior representative.^[14]

The arrangement was significantly expanded by the Takeover Act (Act no. 578 of 24 June 2005), which allows the Faroese government to assume legislative and administrative powers unilaterally across all fields not already within Faroese competence, with the sole exceptions of the constitution, citizenship, the Supreme Court, foreign and defence policy, and monetary policy.^[15][16] Together, the Danish Constitution, the Home Rule Act, and the Takeover Act constitute the Faroe Islands' full constitutional position within the Unity of the Realm.^[15]

Greenland

Greenland obtained home rule on 1 May 1979, following a 1979 referendum in which approximately 70% of Greenlandic voters approved the arrangement. In 2009, the Self-Government Act replaced home rule with a substantially broader arrangement, transferring additional powers including control over Greenland's mineral resources, which formally passed to the Greenlandic government on 1 January 2010.^[17]

Greenland's self-government is considered exceptionally broad by international standards, covering virtually all internal affairs and extendable, in principle, even to areas traditionally regarded as core state functions such as the police, courts, and border control. The Self-Government Act also describes a procedure by which Greenland may declare independence, should its people choose to do so.^[4]

Responsibilities retained by the Danish state

Across the entire realm, the following areas remain under Danish state authority, as preconditions for a unitary state:^[4][15]

• The Constitution of Denmark
• Citizenship
• The Supreme Court of Denmark
• Foreign affairs and security policy
• Defence policy
• Monetary and exchange rate policy

The Danish state provides an annual block grant to both the Faroe Islands and Greenland.^[1] The Prime Minister submits an annual report on the Unity of the Realm to the Folketing.^[1]

World War II: the Kauffmann Agreement (1941)

The German occupation of Denmark on 9 April 1940 created an unprecedented constitutional crisis within the realm. With the Danish government in Copenhagen effectively paralysed under Nazi control, the Danish ambassador to Washington, Henrik Kauffmann, took the extraordinary step of acting independently in Denmark's name. On 9 April 1941 — the first anniversary of the occupation — he signed, on his own initiative and without authorisation from Copenhagen, the "Agreement Relating to the Defense of Greenland" with United States Secretary of State Cordell Hull.^[20] The agreement authorised the United States to establish military bases, aircraft stations, radio and weather stations across Greenland, and to station troops there for the duration of the war.^[21]

The occupied Danish government in Copenhagen declared the agreement void and charged Kauffmann with high treason. Kauffmann disregarded both actions, arguing that a government operating under enemy occupation could not be considered capable of protecting Danish interests.^[20] The agreement was approved by Greenland's own local authorities, and the United States continued to recognise Kauffmann as Denmark's legitimate representative.

Following Denmark's liberation in May 1945, the charges against Kauffmann were among the first matters addressed by the Danish parliament — they were dismissed, and Kauffmann was rehabilitated and appointed to the Cabinet of National Unity. The Danish government formally ratified the 1941 agreement shortly after liberation.^[20]

The Cold War: the 1951 Defense Agreement and Thule Air Base

The end of World War II did not end American strategic interest in Greenland. As the Cold War intensified and the Soviet Union successfully detonated its first nuclear device in 1949, Greenland's position in the high Arctic — lying directly on the polar flight routes between the USSR and North America — made it one of the most strategically significant pieces of territory on earth.

In April 1949, Denmark was a founding member of NATO. Under NATO's direction, Denmark and the United States renegotiated Greenland's defence status, concluding the Defence of Greenland Agreement on 27 April 1951.^[22] The 1951 agreement superseded the wartime Kauffmann agreement, affirmed Danish sovereignty over Greenland, and granted the United States the right to operate military bases and defence areas across the island within a NATO framework.^[23]

The most significant result was the construction of Thule Air Base — today Pituffik Space Base — in the far northwest of Greenland, approximately 1,200 kilometres north of the Arctic Circle. At its Cold War peak, more than 10,000 American troops were stationed there.^[23] Thule functioned as a frontline base for Strategic Air Command bombers carrying nuclear weapons, and American B-52s flew regular missions from and over Greenland throughout the Cold War period. The existence of nuclear weapons at Thule was kept secret from the Danish public and, according to some accounts, from the Danish government itself — a point of lasting controversy in Danish-Greenlandic relations.^[24]

In January 1968, a B-52 carrying four hydrogen bombs crashed near Thule, scattering radioactive material across the sea ice. The accident — known as the 1968 Thule Air Base B-52 crash — became a major political scandal in Denmark, intensifying public debate about the presence of nuclear weapons on Danish territory, which was officially prohibited under Danish policy.^[24]

The 2004 Igaliku Agreement and Greenlandic co-determination

The 1951 Defence Agreement was modified in 2004 by the Igaliku Agreement, signed by Denmark, the United States, and — significantly — by the Greenlandic Home Rule government as a co-signatory. The agreement required the United States to inform both Denmark and Greenland of proposed changes at the base, gave the Greenlandic government the right to appoint its own liaison officer at Pituffik, and required that the Greenlandic flag be flown alongside the Danish and American flags.^[22][25] The inclusion of Greenland as a co-signatory was a notable step in the evolution of Greenlandic self-determination in foreign and security matters.

By 2026, Pituffik Space Base remains the sole active American military installation in Greenland and continues to operate under the 1951 agreement framework. American strategic interest in Greenland has remained intense into the 21st century, including public statements by US President Donald Trump in 2019 and again in 2025 expressing a desire for the United States to acquire Greenland — proposals firmly rejected by both the Danish and Greenlandic governments.^[26]

The Faroe Islands and the EU

The Faroe Islands are not members of the European Union and were not included when Denmark joined in 1973. They maintain a separate trade agreement with the EU.^[1]

Greenland and the EU

Greenland was automatically included in the EC when Denmark joined on 1 January 1973, due to Greenland's then-status as an ordinary Danish county. Following the establishment of home rule in 1979, Greenland held a referendum and voted to withdraw. Greenland formally left the EC on 1 January 1985 — making it the only territory ever to leave a predecessor organisation of the European Union.^[1]

World War II and the 1941 defence agreement

When Germany occupied Denmark in April 1940, the Danish government in Copenhagen was effectively silenced. The Danish ambassador in Washington, Henrik Kauffmann, acting without authorisation from Copenhagen, signed a unilateral defence agreement with the United States on 9 April 1941 — exactly one year after the occupation began — granting the US the right to establish military bases in Greenland in exchange for its protection. The agreement was later ratified by the post-war Danish government. During the war, the US established two large air bases in Greenland, which served as critical refuelling points for military aircraft en route to Europe.^[27]

The 1946 purchase offer

In the immediate aftermath of World War II, as the Cold War began to take shape, the United States made a formal — and secret — attempt to purchase Greenland outright. On 14 December 1946, US Secretary of State James F. Byrnes presented a written offer to Danish Foreign Minister Gustav Rasmussen during talks in New York, proposing the purchase of Greenland for $100 million in gold bullion.^[28] The US Joint Chiefs of Staff had listed Greenland as one of six globally essential strategic locations, and internal American memos described Greenland as "indispensable to the safety of the United States" and "completely worthless to Denmark".^[29]

The offer was rejected by Denmark. Foreign Minister Rasmussen reportedly responded that "while we owe the US a great deal, I do not think we owe them the whole island of Greenland."^[30] The offer remained classified for decades and was first made public in 1991 by a Danish newspaper after the documents were declassified.^[29] Notably, neither the Danish negotiations of 1946 nor the 1941 defence agreement involved the Greenlandic population in any way — Greenland was treated as a Danish colonial possession to be bargained over.^[30]

The 1951 Defence Agreement and Thule Air Base

Although the purchase bid failed, the United States succeeded in securing long-term military access through a different route. In April 1949, Denmark became a founding member of NATO. Building on this alliance, the US and Denmark signed the Greenland Defence Agreement on 27 April 1951, which replaced the wartime 1941 arrangement and allowed the US to maintain and expand its military presence in Greenland under a NATO framework.^[31]

Under the 1951 agreement, the United States was granted the right to establish and operate "defence areas" free from Danish rent or taxation, with US forces permitted to move freely across Greenland's territory and territorial waters. The US military received exclusive jurisdiction over the defence areas, subject to formal recognition of Danish sovereignty.^[23] Between 1951 and 1953, the US constructed Thule Air Base (now Pituffik Space Base) in northwest Greenland, 1,200 km north of the Arctic Circle, requiring 12,000 workers and 300,000 tons of cargo. At its peak, the base housed more than 6,000 American military personnel.^[23]

The 1951 agreement remains in force. The US has since closed all its other Greenlandic bases, and Pituffik Space Base is today the United States Space Force's northernmost installation, housing missile warning radars monitoring the Arctic for ballistic threats.^[23]

The 2004 Igaliku Agreement

A significant evolution in the arrangement came with the Igaliku Agreement of 24 May 2004, signed by the US, Denmark, and — for the first time — the Greenlandic Self-Government as a co-signatory. The agreement amended the 1951 defence treaty to require that the Greenlandic flag be flown over Pituffik alongside the Danish and American flags, and gave the Greenlandic government the right to appoint its own liaison officer to the base. The agreement also established a framework for economic and technical cooperation between Greenland and the United States.^[32] The Igaliku Agreement marked a symbolic shift from a purely bilateral Danish-American arrangement to one in which Greenland itself had a formal voice — reflecting the broader evolution of Greenlandic self-government.

Renewed US interest under Trump (2019 and 2025–)

American interest in acquiring Greenland returned to international attention in 2019, when President Donald Trump proposed purchasing the island. The proposal was rejected by both the Danish government and the Greenlandic authorities, with Danish Prime Minister Mette Frederiksen describing the idea as "absurd".^[33]

Following his re-election, Trump renewed his demands in late 2024 and 2025, stating that US ownership and control of Greenland was "an absolute necessity" for national security, and declining to rule out the use of economic or military force.^[34] In his first speech of 2025, King Frederik X appeared to rebuke the American position, stating: "We are all united and each of us committed for the Kingdom of Denmark, from the Danish minority in South Schleswig and all the way to Greenland."^[33] The Greenlandic parliament issued a joint statement declaring that Greenlanders "do not want to become part of the US" and demanding that the US "show respect".^[33] The Danish Defence Intelligence Service's 2025 threat assessment mentioned the United States as a threat to Danish national security for the first time, alongside Russia and China.^[33]

The episode underscored the central tension within the Unity of the Realm: while Denmark retains formal sovereignty and defence responsibility over Greenland, Greenland itself increasingly insists on acting as an independent voice in matters affecting its own future.