As Russia lays cruel siege to Severodontesk, as the death toll rises and the atrocities drag on, it’s time to ask: How does this war end, or at least reach a cease-fire?

Morally, Vladimir Putin deserves to keep none of his territorial gains. That goes back to his earlier seizure of Crimea and moves into the Donbas. Then, as now, the Russian strongman grabbed his neighbor’s territory with zero justification.

Sadly, those moral claims won’t determine practical results.

Yes, the bravery and resilience the Ukrainians have so far displayed suggest they’re willing to fight on to full victory. But Volodymyr Zelensky and his forces face three crucial limits.

The first is the possibility of Russian escalation. Backed into a corner, Putin truly might be mad enough to go nuclear — betting, say, that using a tactical nuke or two might transform his foes’ calculations.

Second is Ukraine’s lack of resources. Its forces have fought far above their weight, but they depend on the West for materiel.

And that’s the third factor: the willingness of the West, especially the United States, to keep providing the lethal (and non-lethal) aid that lets Ukraine keep fighting. Yes, Washington has committed billions, but America faces its own domestic problems, including an inflation crisis and a midterm election already sucking public support away from US involvement. And several European allies are even shakier.

The West seems willing to back Zelensky & Co. until Putin stops trying to take more territory, but it may well quail at major Ukrainian offensives beyond that.

An actual peace deal looks impossible: Neither Putin nor Zelensky seems willing to settle on a permanent division of Ukraine’s territory, and Putin’s word plainly can’t be trusted anyway.

Indeed, the pre-February status quo seems the very best Ukraine can hope for, and even that could come with carveouts in areas of the country’s energy-rich east that Putin now controls.

But the war needs to end, for everyone’s sake: Ukraine’s civilians and the soldiers on both sides (remember, most ordinary Russian troops are just pawns sent into the meat grinder). As well as the rest of the world: The sudden loss of Ukrainian wheat exports is a huge blow to the global food supply.

Even temporary, internationally unrecognized territorial gains for Putin will be a bitter pill for Ukraine. But the autocrat remains a persona utterly non grata in Europe and America, facing continuing sanctions and general pariahdom. (Indeed, the Ukraine war and its aftermath may well provoke a wholesale rethinking by the West of its entanglement with China, too).

And the US and allies can, must, take real steps to make sure that any future Putin incursion would get stopped cold. That means getting Ukraine enough materiel to make a renewed assault hopeless.

A ceasefire doesn’t mean Ukraine has lost. It means that material necessity has prevailed. Next time, its friends can ensure that necessity is on the right side before the crisis arrives.