Opinion | Realism Must Guide Our Reaction to Russia’s Invasion

Relative to NATO forces, the railway-supplied Russians are short on logistics support and heavy on artillery. Russia’s artillery battalions are the pride of its armed forces, often judged by defense experts to have a qualitative and quantitative advantage over their Western counterparts. As the besieged forces in Kharkiv and Mariupol can attest, the lethality of Russian forces will only rise as this artillery is brought to the front. A slower war of siege and starve may not have been Mr. Putin’s original invasion plan, but it poses severe difficulties for the Ukrainian forces. It is unclear how long forces in Kyiv can withstand a siege. By one American estimate, once Kyiv is surrounded, its food supplies will last for only two weeks. Ukrainian forces in the east face a similar dilemma. If Kharkiv or Zaporizhya falls into Russian hands, the Ukrainians will have to decide between abandoning eastern Ukraine for a more defensible position or risk having their supplies cut off and their position surrounded.

It is unlikely that mounting casualties or temporary logistical frustrations will be enough to force the Russians off the battlefield if either objective — the fall of Kyiv or a Ukrainian retreat from the east — remains in sight. Either will put the Russian forces in a favorable position when peace negotiations begin in earnest. To cease hostilities, the Russians have already demanded that Ukraine recognize the independence of Donetsk and Lugansk, acknowledge Russian sovereignty over Crimea and amend its Constitution to ensure future neutrality. These demands will grow more onerous as the Russian advance creeps forward. Left unspoken in these negotiations is the matter of Western sanctions. Mr. Putin will require at least a partial face-saving victory to end this war. A promise to decrease sanctions might meet this need. This outcome would not be just, but it would hold the best potential for saving the most Ukrainian lives.

Refusal to settle on the part of the Ukrainians or their Western backers will likely lead the Russians to commit to the permanent occupation of the territory they’ve taken. This is the most probable outcome of any policy predicated on inflexible Western ultimatums. In this scenario, sanctions would stay in place for decades. A new iron curtain would fall across Europe, separating Belarus, Russia and occupied Ukraine from the West. Though terrible for the Russian and Ukrainian peoples, this may be a strategically stable and even strategically advantageous state for the United States and its NATO allies.

A Russian economy stalled by sanctions will have trouble funding the expansion and modernization of the Russian military. This diminished Russia, forced to carry the military and economic costs of occupying and pacifying a resistant Ukraine, will find it difficult to repeat its aggression against other recalcitrant parts of the traditional Russian imperium, like Finland and the Baltic States. Maybe the West is willing to accept this outcome, but it carries its own risks.

Trapping a bear makes it more desperate, not less dangerous. Moscow, squeezed by sanctions and facing larger NATO military budgets, may resort to extraordinarily risky measures to forestall decline. It was precisely this logic — complete with the prospect of crushing restrictions by a superior economic power and weapons shipments to a weaker military foe — that led Hitler to Barbarossa and imperial Japan to Pearl Harbor. However, the authoritarian great powers of the 20th century, which gambled that escalating conventional military conflicts might bring Western rivals to the negotiating table before economic isolation reduced their own national power beyond repair, are unlike modern Russia in one key respect: Russia has nukes to gamble with.

This is not a simple problem. Our desire to punish Mr. Putin for the evil he has unleashed in Ukraine must be carefully balanced against the lives that will be lost the longer this war lasts, the real risks of military escalation, the long-term security needs of Europe and the second-order effects a new iron curtain might have on other parts of American foreign policy — such as U.S. security commitments in East Asia and the health of the dollar as the world’s reserve currency. To meet this challenge, we must keep our policy firmly rooted in the “logic of consequence.” Americans living generations from now will be grateful that in this moment of crisis, our policy was guided by careful calculation instead of emotional reaction.