Trump’s Greenland threats have revealed NATO’s defence guarantee only works when the US allows it. Right, so Donald Trump has just done something that exposes a flaw NATO was never meant to show, and it doesn’t go away whether he acts on it or not. Denmark is affected, Greenland is affected, and the alliance that claims to guarantee their security has been forced to sit there while its leader talks about taking allied territory and refuses to rule out force. We’ve seen this pattern before, where sovereignty gets treated as conditional and security gets used as a crowbar, but this time it’s happening inside the alliance itself. Greenland already hosts US forces, already does the job Trump says he “needs very badly,” and yet its leaders are being forced to say out loud that it isn’t for sale. That’s not noise. That’s a system under stress. And the  ...