Trump already has open door to grow U.S. military presence in Greenland thanks to a little-known Cold War-era agreement between the U.S. and Denmark

President Donald Trump’s yearslong threats to take over Greenland have crescendoed this week. On Wednesday, White House press secretary Karoline Leavitt said Trump is considering a range of options in pursuit of the country, and that “utilising the U.S. military is always an option at the commander-in-chief’s disposal.”

But according to foreign policy experts, Danish officials have been baffled by Trump’s threats to resort to military intervention to gain control of Greenland because...