Article 5 of the NATO agreement commits each member state to consider an armed attack against one member state in Europe or North America to be an armed attack against them all. It was acted upon after 9/11 on behalf of the United States by the Balkan countries. The fact that Trump refused indicates his abysmal lack of gratitude. After all it was HIS STATE of New York that sustained the attack. Ungrateful wretch that he is. Disgraceful human being. Shameful. Embarrassing. Inexcusable. Disgusting. :(