Greenland, the world's largest island, is an autonomous territory under Denmark's rule, though it is geographically closer to North America than Europe. While Denmark oversees Greenland's foreign affairs and defense, the United States shares defense responsibilities under a 1951 treaty and maintains an air force base on the island.

President-elect Donald Trump hasn’t ruled out military action in what some call a far-fetched pledge for control of Greenland. Here’s why any bid for the Danish territory is complicated and controversial.