Nato said on Tuesday that military planning has started for a new mission to bolster security in the Arctic, after US President Donald Trump made protecting the region central to his demands for Greenland. “Planning is under way for a Nato enhanced vigilance activity, named Arctic Sentry,” said Martin O’Donnell, a spokesman for Nato’s Supreme Headquarters Allied Powers Europe. “The activity will even further strengthen Nato’s posture in the Arctic and High North,” he added, without providing...