A deal for peace in the Ukraine war threatens to unite major NATO nations in the kind of alliance that President Putin has long feared.

It’s for that reason that one of Mr. Putin’s closest aides and confidantes, Dmitry Medvedev, rules out any possibility of troops from Europe patrolling Ukraine in a peace-keeping force after the signing of an armistice.

Mr. Medvedev, who once served as president of Russia while Mr. Putin was prime minister in between stints as president, poured cold water on the concept of a “coalition of the willing” to be sent to Ukraine to guarantee peace. Only nations not associated with the NATO alliance could be peace-keepers, he made clear.

For Mr. Medvedev, the most obvious drawback would be that any deal that permits European members of NATO to give arms to Ukraine while Russians are still there would be dead before it even went up for serious discussion. That kind of cooperation by NATO members would mean “war with NATO,” he wrote on X.

For Mr. Putin to order his troops to confront the peace-keepers from European countries would risk a sharp escalation in the fighting regardless of the veneer of peace-keeping shrouding their presence in Ukraine. The major European players, Prime Minister Starmer and President Macron, have been trying to allay Russian concerns, stressing that the force would total at most 30,000 men whose intention would be to make sure the fighting did not flare up again.

The fighting, though, could well escalate if Mr. Putin hankers to nip off more of Ukraine.  A major reason he might try to do just that is the pivotal role that North Korean troops are playing in driving the Ukrainians out of much of the Kursk oblast that they had overrun across Ukraine’s eastern border.

Now the North Koreans, bloodied but easily replaced at leader Kim Jong-un’s snap of the fingers by more from his military establishment of 1.2-million troops, may be poised to drive deep into Ukraine.

The North Koreans “started making incursions into Ukraine in August,” the managing editor of the website NK News, Bryan Betts, tracking North Korea from Seoul, said during a podcast. “They were the main assault troops suffering the heaviest casualties” — at a ratio of 50 North Koreans to six Russians.

With the North Koreans ready “to play a much more offensive role,” Mr. Betts said he is sure their performance will be “influencing” talks on any “peace.” Complicating matters is that neither Mr. Putin nor Mr. Kim acknowledge the role of the North Koreans, who wear Russian uniforms, carry Russian gear, and are issued Russian identification cards. 

Europeans would provide the guarantee that President Zelensky has said he needs for a cease-fire to hold.

Mr. Putin has told President Trump in a telephone hook-up that a cease-fire would be fine provided the Ukrainians just stop fighting. That’s not likely to happen, though, without the guarantee that Mr. Zelensky, in his infamous White House meeting with Mr. Trump and Vice President Vance, said he needed.

So far, European countries have not come up with a coherent plan for keeping the peace along Ukraine’s 670-mile border with Russia. The most enthusiastic appear to be Britain, which Mr. Starmer has said might base 10,000 troops there,  and France, where Mr. Macron has talked of deploying “several thousand.” Others, ranging from Australia to Canada, from Portugal to Belgium, have seemed open to the idea.

Gradually, though, the European powers, without Washington, appear ever more interested in keeping the peace in Ukraine out of concern the Russians may expand their drive into the heart of Europe — the same fear that led to the rise of NATO. 

Meeting at London, they agreed on the need to “accelerate our military support, tighten our sanctions on Russia’s revenues, and continue to explore all lawful routes to ensure that Russia pays for the damage it has done to Ukraine,” the BBC reported. Mr. Zelensky was more menacing. “The path to peace must begin unconditionally,” he said. “If Russia doesn’t want this, then strong pressure must be applied until they do.”