Across several years and political seasons, Donald Trump returned again and again to a single, striking proposition: that the United States should acquire Greenland. What began in 2019 as a remark that seemed to belong to the realm of the eccentric gradually revealed itself as a sustained strategic conviction — a signal that American attention was turning northward, toward an Arctic increasingly contested by great powers and reshaped by a warming planet. The persistence of the idea, more than the idea itself, became the story.