If you want a serious intra-conservative debate on U.S. aid to the Ukrainian war effort, I highly recommend listening to my colleagues Noah Rothman, Charlie Cooke, and Michael Brendan Dougherty on The Editors, a debate continued at director’s-cut length on Charlie’s podcast. I side mostly with Noah and Charlie — Michael is outnumbered here at National Review in opposing aid — but it’s a rigorous and passionate debate on both sides.

Let me address one thing Michael said. It’s common ground that one of the important things at stake in the Ukraine conflict is the credibility of the United States, the NATO alliance, and the wider American-led liberal order that has governed the non-Communist world since 1945 and has extended to the old Warsaw Pact and many of the former Soviet republics since 1991. Both Michael and Noah agreed that it is vital for America and its allies to preserve credible deterrence in order to keep Russia, China, and other bad actors from using force or the threat of force to seize or extort concessions.

Michael’s position, explicitly stated, is that the U.S. and NATO do more damage to their credibility by fighting Russia in Ukraine and losing than by not fighting at all and letting Russia win. (“Fighting” here refers to a proxy war conducted by the Ukrainians but financed and armed by the West.) His reasoning, if I can fairly summarize it, is that we are unnecessarily dissipating our credibility by staking it on a fight we are likely to lose — and that our defeat would add to Russian prestige, detract from our own, and lead Russia’s neighbors to readjust their behavior to Moscow’s benefit as they come to see Russia as more of a strong horse and the Western alliance as more of a paper tiger.

I disagree.

It is surely true, as Noah argued vigorously, that a Russian victory in Ukraine would have some of those bad effects and that it would be considerably worse for us than a Ukrainian victory (which includes peace on terms that preserve Ukraine’s sovereignty in a meaningful sense). Where I part company from Michael is that I think it would be more damaging to our credibility to do nothing (and even worse, having begun to fight, to pull the plug on the Ukrainians). Deterrence has three components that, taken together, convince an adversary that it is not worth the cost of provoking you:

It’s true that the U.S. and NATO do not respond to every provocation around the world, such as wars between small nations in which we don’t have a particular interest or provocations that we see as too petty to merit any response. But this provocation was very large: a massed infantry and armored invasion of a sovereign state of some 40 million people. It’s a provocation not by some peripheral actor but by Russia, one of the very adversaries that we are most interested in deterring — the adversary that NATO essentially exists to oppose — which is part of a broader axis with China and Iran. It’s geographically on the doorstep of NATO: Five NATO nations shared a border with Russia at the beginning of this war (now six do, with the accession of Finland), three others share a border with Ukraine, and two more have coastlines on the Black Sea. Ukraine’s strategic location made it the site of significant combat in the Second World War and the main locus of the largest multipolar European war between 1815 and 1914. It was already a key focus of U.S. and NATO foreign policy for a decade and a half before the invasion and the recipient of significant military aid. It’s also one of the test cases for whether it’s rational for midsize nations to voluntarily abandon their nuclear arsenals. Ukraine, which had the world’s third-largest nuclear force at the time, abandoned it in 1994 in exchange for pledges by the U.S., the U.K., and Russia (among others) “to respect the independence and sovereignty and the existing borders of Ukraine.” In short, this is exactly the sort of provocation in size, proximity, and area of interest that a power such as Russia should fear to undertake and will conduct if it thinks it can do so without suffering a serious penalty inflicted by the West.

Everybody understands that the Achilles’ heel of the United States and its alliances is the will to fight and the will to continue — not the capacity. If Russia was able to invade Ukraine without serious consequence from us, the perception of our weakness of will would be apparent. The same would be true if we fail to continue. We have seen an escalatory pattern: When we didn’t resist Russia’s invasion of Georgia in 2008, it followed up by invading Ukraine and taking Crimea in 2014. When we didn’t resist that, either, Russia escalated again with the current war, commenced in February 2022.

A failure to see things through would be a blow as well to our credibility because it would deepen perceptions that one can beat America and its allies by outlasting them in terms of willpower. Among wars we fought ourselves, that’s how we lost Vietnam and Afghanistan: We first pulled out and then left our erstwhile allies to the mercy of their enemies. I take Michael’s point that engaging in the war runs the risk that we end up bailing out and showing yet again that our will to fight can be outlasted, but we can avoid that end simply by continuing to support the Ukrainians so long as they are willing to keep fighting — and doing so while continuing to aid Israel and Taiwan.

But what if we stay that course and lose? That proves that our proxy, Ukraine, was no match for Russia in the end — at least not without direct NATO military involvement, which almost nobody wants. But it says nothing about anyone’s capacity to defeat the United States or NATO when it is provoked in a way that does result in direct involvement. That’s especially the case when one considers that some of Ukraine’s military failings have been the result of its lacking the military culture and training to properly operate NATO weapons in combined-arms warfare.

And in deterrence terms, this war has unquestionably been much costlier to Russia in men, arms, and money than it would have been had the U.S. and its allies simply stood aside. It has also been diplomatically costly to Russia with the accession of Finland and Sweden to NATO. After more than two years of war, the lesson is not remotely lost on Moscow or Beijing that this has turned out to be much harder and more painful than expected. Imperial overstretch is a two-way street, and Russia is feeling its costs just as we did when we fought, and won, the war in Iraq, or when the French fought, and won, a war to detach Britain’s American colonies. If we wish to deter even graver provocations, the costs and lessons we’ll have imposed on Russia would not be lessened, even if, in the end, Russia proves simply too strong for Ukraine.