President Donald Trump and members of his Cabinet have made a case for acquiring Greenland that’s so simple, even self-evident, it seems hard to refute: U.S. national-security interests in the Arctic are just too important to ignore. Not taking over the autonomous territory of Denmark would “give up the Arctic to China, to Russia, and to other regimes that don’t have the best interests of the American people at heart,” Vice President J. D. Vance declared last March during a visit to the Pituffik Space Base, on Greenland’s northwest coast. Five years ago, Congress had a similar sense of alarm about Russia and China’s head start in exploring and potentially developing one of the world’s last great untapped regions, with its rich minerals, abundant (if icebound) seas, and strategic location almost connecting the continent of Europe with the northernmost reaches of the Americas. The 2021 National Defense Authorization Act called for the creation of the Arctic and Global Resilience Policy Office at the Pentagon, which was set up in 2022. The office produced the Defense …