Denmark has confirmed a Cold War–era military rule requiring its soldiers to immediately counterattack any invading force without waiting for orders — a policy that remains active today. The revelation comes as U.S. President Donald Trump renews talk of annexing Greenland, a Danish territory, citing American national security interests. The comments have shocked Denmark, Greenland’s government, and NATO allies, triggering urgent discussions across Europe. Officials warn that a U.S. move against Greenland could mark an unprecedented crisis within NATO, raising fears of a historic rupture in transatlantic relations and European sovereignty.