Moreover, no one should put much faith in the recently enacted Congressional edict meant to prevent a president from withdrawing from the alliance without Congress’ consent either. No one can force an American president to defend another country with the full force of the U.S. military — not even Congress.
Legally, the U.S. (or any other NATO member, for that matter) is merely obliged to take “such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.” In other words, each member is left to decide for itself whether and how to act in case of an armed attack on an ally. And even that provision, in Article 5, is only binding after all NATO members agree to invoke the commitment.
What makes a security alliance effective isn’t some legal diktat, however — it’s the trust that allies have in each other, that they will come to each other’s defense, and the credibility of that commitment in the eyes of their adversaries. Legally binding commitments can solidify that trust, but they can’t sustain it on their own — let alone build it.
But whether Trump would actually withdraw from NATO as many fear — which any treaty ally can do under Article 13 — is beside the point. The simple fact is that his reelection would be seen as a fundamental repudiation of the trust NATO allies have placed in the U.S. to come to their defense in case of an armed attack. More so, now that the possibility of such an attack looms large in Europe after Russia’s brutal war in Ukraine. Neither allied leaders nor their publics would have any confidence that a Trump-led America would come to their aid.
This reality wouldn’t necessarily spell the end of NATO, though it would turn it into a fundamentally different alliance than the one that’s existed for the past 75 years. NATO wouldn’t end even if he were to formally withdraw — it would just have one less member.
Of course, the U.S. isn’t like every other NATO member — it’s the true backbone of the alliance. Starting with General Dwight D. Eisenhower, its supreme commander has always been American. The U.S. military also accounts for a good part of NATO’s overall capability, and its armed forces constitutes the nucleus around which most NATO allies have built their own militaries. More than 100,000 U.S. land, air and naval forces are currently deployed throughout Europe in direct support of NATO.