FACTBOX | An overview of military assets in the Arctic

United States and Canada

Since 1957, the US and Canada have jointly defended against threats to their homeland, including from nuclear missiles, via the North American Aerospace Defence Command, known as NORAD.

They are modernising NORAD, according to the IISS: Canada is procuring two over-the-horizon radar systems covering the Arctic and polar approaches, with the first due to reach initial operating capability by 2028.

President Trump is keen to develop a new missile defence system, called Golden Dome, for which he says Greenland is crucial.

Washington has the Pituffik Space Base in northern Greenland under a defence agreement with Denmark. Otherwise, most of its Arctic forces are located across eight bases in Alaska and count approximately 22,000 military personnel, according to IISS and the US Northern Command.

Canada has five Arctic bases, including Alert, a signals intelligence station on Ellesmere Island that is the world's northernmost permanently inhabited settlement.

South of the Arctic Circle, Canada operates a base at Yellowknife in the Northwest Territories, which hosts a ranger patrol group and an air base.

Canada is building a facility on Baffin Island to refuel offshore patrol ships - though the project has sustained numerous delays. The US, meanwhile, is expanding existing port facilities at Nome, Alaska, according to IISS.