Opinion: There are two endgames in Ukraine. Both carry big risks.

Last week brought a little clarity to the fog of the Ukraine war: The significant date of May 9, the celebration of the Soviet Union's victory over Adolf Hitler's Germany, came and went with no change of Russian strategy.

When Vladimir Putin came out to inspect the military parades and intercontinental ballistic missiles, there was neither a declaration of pseudo-victory nor an announcement of escalation that would have put all of Russia on a war footing and begun mass conscriptions for the front. More of the same, then, seems to be the Russian plan - meaning a continuation of the grinding war in Ukraine's south and east, with the goal of regime change essentially abandoned in favor of the goal of holding territory that might eventually be integrated into the Russian Federation.

From the American perspective, this looks like strategic vindication. We have steadily escalated our support for Ukraine - including the $40 billion package that will probably clear the Senate this week - without provoking reckless escalation from Russia in response.

Two scenarios loom for the next six months of war. In the first, Russia and Ukraine trade territory in small increments, and the war gradually cools into a "frozen conflict" in a style familiar from other wars in Russia's near abroad.

Under those circumstances, any lasting peace deal would probably require conceding Russian control over some conquered territory, in Crimea and the Donbas, if not the land bridge now mostly held by Russian forces in between. This would hand Moscow a clear reward for its aggression. And depending on how much territory was ceded, it would leave Ukraine mutilated and weakened, notwithstanding its military success.

There is another scenario, however, in which the stalemate breaks in Ukraine's favor. This is the future that the Ukrainian military says is within reach - where with sufficient military aid and hardware it is able to push the Russians back not just to prewar lines but potentially out of Ukrainian territory entirely.

Clearly, this is the future America should want - except for the extremely important caveat that it's also the future where Russian nuclear escalation suddenly becomes much more likely than it is right now.

We know that Russian military doctrine envisions using tactical nuclear weapons defensively, to turn the tide in a losing war. We should assume that Putin and his circle regard total defeat in Ukraine as a regime-threatening scenario. Combine those realities with a world in which the Russians are suddenly being routed, their territorial gains evaporating, and you have the most nuclear-shadowed military situation since our naval blockade of Cuba in 1962.

I've been turning over these dilemmas since I moderated a recent panel at the Catholic University of America with three right-of-center foreign policy thinkers - Elbridge Colby, Rebeccah Heinrichs and Jakub Grygiel. On the wisdom of our support for Ukraine up till now, the panel was basically united. On the question of the war's endgame and the nuclear peril, however, you could see our challenges distilled - with Grygiel emphasizing the importance of Ukraine's recovering territory in the east and along the Black Sea coastline in order to be plausibly self-sufficient in the future, but then the more hawkish Heinrichs and the more cautious Colby sparring over what our posture should be in the event that rapid Ukrainian advances are met with a Russian tactical nuclear strike.

That question isn't the one immediately before us; it will only become an issue if Ukraine begins to make substantial gains. But since we are arming the Ukrainians on a scale that seems intended to make a counteroffensive possible, I sincerely hope a version of the Colby-Heinrichs back-and-forth is happening at the highest reaches of our government - before an issue that matters now on academic panels becomes the most important question in the world.

The New York Times

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