Greenland has emerged as one of the world’s most strategically contested territories. The Arctic island’s vast rare-earth mineral reserves and location amidst newly opened polar shipping lanes are reasons U.S. President Donald Trump has long said that owning it is key for American security and economic interests. At the January World Economic Forum in Davos, after early threats of taking the territory by force and levying tariffs on European countries who stood in his way, Trump walked back those threats, but announced that talks were underway on a possible framework. In this exclusive excerpt from Polar War: Submarines, Spies, and...