Three months ago, Ukraine would have likely ceded de facto control of roughly the same amount of real estate Russia now controls to end the war. After watching Russia squander men and equipment through bad leadership, poor training, and inexplicable failures of basic combined arms, that calculus would have to change, politically at least.

And it has, the New York Times reports this afternoon. Now it’s Ukraine issuing the ultimata rather than Russia. Perhaps more accurately, Kyiv is issuing the credible ultimata:

Vladimir Medinsky, the head of President Vladimir V. Putin’s delegation, speaking in his first interview with a Western news outlet since the beginning of the war, has claimed that Russia has still not received a response to a draft peace agreement that it submitted to Ukraine on April 15. Rustem Umerov, a top Ukrainian negotiator, responded by saying that Russia was operating with “fakes and lies.”

“We are defending ourselves,” Mr. Umerov said in an interview. “If Russia wants to get out, they can get out to their borders even today. But they are not doing it.”

On Tuesday, both sides further played down the prospects of a deal. Another Ukrainian negotiator, Mykhailo Podolyak, issued a statement saying that the talks were “on pause” and that given Russia’s faltering offensive, the Kremlin “will not achieve any goals.” And Andrei Rudenko, a Russian deputy foreign minister, told reporters that “Ukraine has practically withdrawn from the negotiating process,” the Interfax news agency reported.

Why would Ukraine have snubbed a Russian peace proposal on April 15? For one thing, that “peace” proposal was more of an ultimatum that would have severed the Donbas and Crimea permanently from Ukraine. Negotiators didn’t bother to brief Volodymyr Zelensky on the terms, knowing that the situation on the ground had changed enough to make those terms impossible for Zelensky to accept in political terms. The Ukrainian army had driven Russia from Kyiv and the north, and Russia had already begun to bog down elsewhere.

One month later, the situation has changed significantly — in Ukraine’s favor, for the most part. It now has a massive influx of superior weaponry coming from NATO members, including the US, plus superior intelligence. Russia still hasn’t achieved air superiority, and it keeps making catastrophic tactical moves that waste their dwindling supplies of men and materiel. That makes it even more difficult for Zelensky, ironically:

The impasse stems primarily from Russia’s insistence on maintaining control of large swaths of Ukrainian territory, and Mr. Putin’s apparent determination to push ahead with his offensive. But another factor is an emboldened Ukraine: Its successes on the battlefield, combined with anger over Russian atrocities, have the Ukrainian public less willing to accept a negotiated peace that would keep a significant amount of land in Russian hands.

A few weeks ago, a grinding ground-forces fight looked like it would favor Russia. No longer; the Russians’ ability to maintain their lines even in areas of relative strength in the southeast appear to be eroding. Their spectacular failure around Kharkiv poses a real threat to their flank, and eventually Ukrainians will find holes in the demoralized lines to split and then demolish entire Russian formations.

That ability comes as a direct result of NATO’s intervention. Again ironically, that leaves the politics of peace talks very brittle for Zelensky, even if they have suddenly become a lot more flexible for Putin, whose alliances are already fraying over Ukraine. The lessons of Michael Collins are likely too apparent to Zelensky to allow Putin any easy face-saving exit from Ukraine after three months of Russian brutality. Realistically, while Ukraine keeps getting arms and keeps pushing Russia around, his only way forward for now would be to force Putin to allow the clash of arms to settle Ukrainian sovereignty once and for all.

Of course, this leaves Zelensky at the mercy of NATO. If we go wobbly, so to speak, we could cut off that flow of arms as a way to force Zelensky into concessions that will end the war in Europe before it spreads. That risk alone might convince Western countries to start applying that pressure if Russia would agree to a status quo ante.

Garry Kasparov realizes that too, and warned against it last night:

There are still signs that some Western leaders haven’t yet learned that isolating Mr. Putin and responding to him with strength is the only way to make lasting progress. French President Emmanuel Macron spoke last week about the need to negotiate with Mr. Putin, to give him face-saving off-ramps. Defense Secretary Lloyd Austin called his Russian counterpart Friday to urge a cease-fire, potentially leading to the sort of “frozen conflict” Mr. Putin loves because he simply ignores the restrictions while consolidating and rearming.

I’ve long said that Mr. Putin is a Russian problem and must be removed by Russians. But the West needs to stop helping him. Every phone call that legitimizes his authority, every cubic meter of gas and every barrel of oil imported from Russia is a lifeline to a dictatorship that is shaking for the first time.

If the goal is to save Ukrainian lives, as Western leaders say, then the only way to do it is to arm Ukraine with every weapon President Volodymyr Zelensky wants as quickly as possible. A cease-fire that leaves Russian forces on Ukrainian soil would only allow Mr. Putin to continue his genocide and mass deportations under cover, as he’s been doing since he first invaded in 2014. …

We will see how committed Ukraine’s allies really are as the war moves into a new phase in which defense is not enough. Will they help Ukraine win, to destroy Mr. Putin’s war machine, and to restore all Ukrainian territory? Will they keep sanctions in place to increase domestic pressure on Mr. Putin and to let his mafia know that there is no way back to the civilized world for them and their families while Mr. Putin is in power?

Kasparov has a good read on the situation, and perhaps a good read on the West’s perseverance. Until we actual quail and go wobbly, however, Zelensky doesn’t have any choice but to keep pressing the war. And Putin may have no choice but to head to the borders while he still has a military that can defend Russian territory on the suddenly expanded NATO frontiers.