'Unthinkable': How Trump could use 'veto power' for 'terrifying' violation of NATO's Article 5

President Donald J. Trump participates in an official welcome ceremony Wednesday, Dec. 4, 2019, with the Secretary General of the North Atlantic Treaty Organization (NATO) Jens Stoltenberg and the British Prime Minister Boris Johnson at the 70th anniversary of NATO in Watford, Hertfordshire outside London. (Official White House Photo by Shealah Craighead)