Over a year since US President Donald Trump began his second term and revived threats of an American takeover of Greenland, the US and Denmark on Friday (September 18) announced a deal on Greenland’s security.Greenland is a self-governing territory within the Kingdom of Denmark. Under the 2009 Self-Government Act, its government exercises wide legislative and executive powers, while Greenlanders retain the right to determine the island’s future.BREAKING NEWS: I am pleased to announce that the United States of America has entered into an Agreement with The Kingdom of Denmark, and Greenland, that gives the United States permanent control over security, and all other needs, in Greenland, completely addressing ALL of our…— Donald J. Trump (@realDonaldTrump) September 19, 2026While Trump said the agreement, which will be signed next week, will grant the US “permanent control over security, and all other needs”, Denmark offered a narrower description.Denmark’s Prime Minister Mette Frederiksen said the deal “strengthens security in the Arctic and the North Atlantic area,” while explicitly reaffirming the sovereignty and territorial integrity of the Kingdom of Denmark and Greenlanders’ right to self-determination.The agreement is expected to be signed next week at the UN General Assembly, and will enter into force only after the necessary parliamentary procedures. We explain.What has actually been agreed?While the full text of the agreement has not been made public, statements released by the US and Denmark indicate that the deal would give the US permanent security access in Greenland while leaving Danish sovereignty intact.Trump said the US would have the ability to do what it considered necessary for Greenland’s defence and security, and that adversaries would be barred from establishing bases, a military presence or making sensitive investments there without US approval.Denmark, on the other hand, described the deal as strengthening security in the Arctic and North Atlantic, while reaffirming the sovereignty and territorial integrity of the Kingdom of Denmark and Greenlanders’ right to self-determination.So what actually changes for the US?Story continues below this ad FILE — Crowds gather and wave the flag of Greenland to protest President Donald Trump and his proposal to take over Greenland, in Nuuk, Jan. 17, 2026. (Juliette Pavy/The New York Times)The US already had very broad military access to Greenland under the 1951 defence agreement, including free movement between defence areas by land, sea and air. US aircraft could overfly and land in Greenland subject to the agreement. The agreement remains in force.Those rights were not unlimited. New US defence areas or facilities still required agreement with Denmark, and the 2004 update designated Pituffik, then Thule Air Base, as the US defence area while creating consultation mechanisms with Greenland’s government.That means Trump’s description of the new deal as “permanent control” may overstate how much has changed in practice. The US already had a military presence, access to Greenlandic airspace and the ability to operate Pituffik.According to Reuters, the new agreement would make US access, basing and overflight rights permanent, including if Greenland’s political status changes in the future.Story continues below this adTrump has separately said that US adversaries would be barred from establishing bases, maintaining a military presence or making sensitive investments in Greenland without Washington’s approval.How much additional freedom Washington gets to expand its military footprint remains unclear until the agreement is published. If new bases still require Danish and Greenlandic consent, the practical military change could be limited. If Washington gains unilateral authority over new facilities or investments, it would be much more significant.How much access did the US already have in Greenland?The US has long expressed varying degrees of interest in possessing and controlling the territory. In 1867, then US Secretary of State William Seward explored the possibility of acquiring Greenland and Iceland, although Washington never made a formal claim.During World War II, after Nazi Germany occupied Denmark, the US entered into a 1941 agreement that allowed it to establish airfields and other defence facilities in Greenland while recognising Danish sovereignty over the island. After the war ended, US President Harry S Truman in 1946 offered $100 million to Denmark for Greenland, after previously considering exchanging some portions of Alaska for parts of Greenland.Story continues below this adIn 1951, the US entered into a defence agreement with Denmark, allowing it extensive military access across Greenland and the right to establish agreed defence areas. It was later supplemented by a 2004 agreement, which designated Thule Air Base, now Pituffik Space Base, as the only US defence area in Greenland.Why does the US want a Greenland presence?American interest in Greenland is rooted in geostrategy.From a military standpoint, Greenland’s location is significant, serving as a vital base of operations during the Cold War (1945-91). The US operates the sprawling Pituffik Space Base, which hosts an early-warning radar system used by the US and NATO to detect missile threats and monitor activity in the Arctic.Its location between North America and the Arctic also makes Greenland important to US plans for monitoring Russian and other military activity in the region. In recent years, China and Russia have reportedly scaled up their military capabilities in the Arctic, according to an Arctic Institute research paper.Greenland also has large deposits of rare earth elements and other critical minerals, which are extensively used in mobile phones, electric vehicles and other consumer electronics, as well as in bombs and other weapons. China is currently the leading supplier of many rare earth elements globally.Story continues below this adGreenland’s mineral wealth has therefore become part of the wider strategic competition over critical-mineral supply chains. In 2021, Greenland banned mining of deposits containing uranium above a specified threshold, a decision that stalled development of the large Kvanefjeld rare-earth project.