Europe builds better defenses Collapse In the run-up to NATO’s largest military exercises since the Cold War, a top European commander was asked what might happen if the United States quits the alliance. In the face of wavering Western support for Ukraine, the alliance has been using these war games to suss out and strengthen its shortfalls. These are key steps, analysts say, in bolstering the credibility of an alliance that might one day have to survive without U.S. backing.