Greenland became a strategic prize during the Second World War, when the United States occupied the island to block Nazi advances, shield Atlantic convoys and gather the meteorological intelligence that helped time D-Day. It later formed the backbone of NATO’s Arctic early-warning system during the Cold War. Trump’s latest claim that America “has to have” Greenland has revived that history, alarmed Denmark and unsettled the alliance. Yet Greenland’s future remains a matter for Greenlanders, not Washington, writes historian Dr Linda Parker