The real question is whether the United States has a strategic stake in Ukraine at all. The answer is yes.
Most tangibly, a quick glance at a map shows that Ukraine borders no fewer than five NATO countries. Poland, Slovakia, Hungary, Romania, and Bulgaria would all have Russian troops on their doorsteps if Ukraine were to fall. When Moscow says it wants Ukraine demilitarized, it is unlikely that it is including its own forces in the equation. What would be the impact on the political and military posture of the countries on that new front line? No one knows, and no one should want to find out. On the other hand, the survival of free Ukraine would deprive Russia of not only the proximity but population and resources that it would use to threaten its neighborhood, and us. It was, above all, the loss of Ukraine that disemboweled the Soviet Union, and reattaching Ukraine is a prerequisite for the full revival of the Russian Empire. Altogether, if we are, by necessity, back to containment, containment with Ukraine as part of the West is to be vastly preferred over containment with Ukraine under Moscow’s control.
In the longer term, if Russia is successful in Ukraine, it will surely conclude that it can press forward at some new perceived weak spot. Critics dismiss this danger, as they dismiss the broader imperialist motivations behind Putin’s actions. Russia, the argument goes, lacks the military resources to go further. True, for today—largely because the aid we are giving Ukraine is significantly degrading Russian military capabilities. But tomorrow? Conquest, as military strategists have long observed, does not hinge on numbers. It hinges on numbers multiplied by will. If the United States and its allies abandon the Ukrainians to their fate, why would Putin not make the calculation again, once his forces are replenished, that he has enough numbers to enforce his will against spineless opponents?
This analysis would argue for expanding Western military aid to supply more and better weapons, including weapons denied to the Ukrainians so far. The Soviets, after all, supplied North Vietnam with modern tanks, MiGs, and state-of-the-art surface-to-air missiles without triggering World War III.
Would this mean reinforcing failure, as some have suggested? It has been six months since Russia launched its full-scale invasion. It has not been bankrupted nor has its army collapsed in disgrace. But who, on February 24, would have counted it a failure for Ukraine to still be standing today, having held the line, driven the Russian army back from Kyiv, neutered the Black Sea Fleet, retaken wide swaths of territory, and even struck deep into Crimea? What realistic person would have counted the sanctions a failure if their effect was to reduce Russia to firing anti-aircraft rockets at cities? Almost no one. It is not failure that we need to reinforce. It is incomplete success.