Earlier this month, three U.S. Navy destroyers and a British warship conducted an exercise in the frigid waters of the Barents Sea, the first time U.S. surface ships have ventured into Russia’s Arctic backyard since the mid-1980s.

It comes as global warming is melting the polar ice cap, opening new sea routes and increasing competition for oil and mineral resources, with Russia, in particular, aggressively seeking to assert its preeminence in the region.