NATO isn’t as vital as it was during the Cold War — institutions inevitably change over time — but it still matters. Maintaining the alliance and the current European order are clearly in the national-security interests of the United States. It’s an enormous strategic benefit to us to have a vast zone in Europe of allied countries that are prosperous, free, and at peace, and that look to us for leadership.

It speaks to the alliance’s continued deterrent effect that Putin is, notably, not threatening a NATO country. The alliance has provided military support in Afghanistan and for post-9/11 counterterrorism missions. It is a force-multiplier for us to train with and to be interoperable with European forces. Finally, NATO provides a political cohesion that is going to be increasingly useful in resisting Chinese efforts to exploit divisions in Europe.

If Russia resorts to naked aggression in Ukraine and gets away with it, it will be a blow to the post–Cold War order in Europe. And if the U.S. ever gives up on NATO, it will undermine all our other commitments around the world and pave the way for China to supplant the U.S. as the world’s predominant power.