President Joe Biden wrapped up his three-day trip to Ukraine and Poland Wednesday with a meeting of the “Bucharest Nine” — leaders of nations on NATO’s eastern flank. Biden pledged the U.S. would invoke Article 5 of NATO’s Charter, the “collective self-defense” clause, if any member is attacked. 

President Joe Biden: “Article 5 is a sacred commitment the United States has made. We will defend literally every inch of NATO. Every inch of NATO.”