US President Donald Trump's proposals to acquire Greenland have prompted strong reactions from European allies, with Denmark's Prime Minister stating such a move would be 'the end of Nato.' The article traces Nato's origins to the post-WWII era, formed by Western democracies to counter the Soviet Union with a collective defense pledge under Article 5. It notes the alliance's expansion and the Soviet response with the Warsaw Pact, highlighting current internal strains testing the alliance's core principles.