A good idea months ago would have been pushing aside Russia’s gossamer, largely hypothetical military blockade of Ukraine’s ports. The West finally had a chance this week when Vladimir Putin sought to revive the illusion of a blockade in Western minds by backing out of a U.N.-sponsored grain-shipping agreement.

Result: He climbed down when other parties decided the ships would sail anyway.

Lesson: Pay due regard to Mr. Putin’s well-honed capacity for retreat.

Elon Musk and progressive Democrats have also learned a useful lesson lately. Nothing is more personally gaseous than to be heard calling for negotiations when the moment is unripe.

Most interesting is the fallout from a now-withdrawn letter by House progressives urging negotiations on the Biden administration. Our elites aren’t as incompetent as they seem. Ninety-nine percent of the people in Washington know their jobs well enough to know the letter was a bad idea.

The same is true of House Republican Leader Kevin McCarthy’s unnecessary statement that Ukraine won’t get a blank check, not that anybody advocated a blank check. Nothing in the letter or Mr. McCarthy’s statement needed to be said now or at all. The episodes served only as a signal to Mr. Putin to keep doing what he’s doing because it’s working—a signal that collective Washington came together to rescind.

That said, an ugly deal still may be coming. It may be more or less ignominious. It may be more or less favorable to Ukraine’s interests. To those who fret about a wilting of Western resolve under energy or inflationary pressure, one comfort will be: No settlement now can save Mr. Putin from being deeply underwater on his Ukraine venture. It’s been a debacle. Nobody envies his position, admires his judgment or thinks his military is competent.

Joe Biden wonders what off-ramp Mr. Putin sees for himself, as if the Russian leader could hope to pull a real-world rabbit out of a real-world hat. He needs a TV rabbit and TV hat, ones he can present back home as a resolution, likely involving some cosmetic concession to the Kremlin’s varying and inconsistent claims about how Ukraine endangers its vital interests.

Mr. Biden perplexingly also suggested that any use of a nuclear weapon must lead to Armageddon. In reality, nobody is obliged to do any particular thing if Russia were to detonate a nuke in Ukraine.

And depending on the details, the right response might be to keep on keeping on. That said, while interpreting Mr. Biden remarks is risky, he may have sent a useful signal to Mr. Putin that, no, detonating a nuke won’t get you negotiations on terms you will like.

Mr. Putin’s situation is not Hitler’s; invading armies aren’t laying waste to his country, looking to drag him back to Stalin for interrogation and show trial.

Ukraine understandably might wish to see Russia transformed, broken up, subjected to a revolution—but a Ukrainian army won’t be rolling into Moscow to make it happen.

Nothing in the present scenario points to nuclear war between superpowers as much as many find it useful to invoke the risk of nuclear war as negotiations begin to shimmer in the distance.

Perhaps less than serendipitously, a fairly conventional new history of the Cuban missile crisis by Max Hastings has been landing in pundit inboxes. Spare a moment for last year’s account of the same episode by Ukrainian historian Serhii Plokhy. It contains a fetching account of dealings between Bobby Kennedy and the KGB’s Yuri Barsukov in the 1960 election, which later had Khrushchev bragging to a scientific delegation that he elected JFK.

The book shows, with accidents and confusion happening all around them, the protagonists still trying to understand each other’s political needs as the missile crisis unfolded. Recall that Kennedy controlled the war decision, with his threat of invading Cuba, at a time when he knew the U.S. possessed overwhelming nuclear superiority.

Kennedy wanted to avoid nuclear war as much as Khrushchev did, but still nuclear war was a more plausible option for one party than it is for either today.

Of course, the big lacuna in deterrence theory is how to deter the idiot or, say, the leader who badly understands his own position. In ways we may never know, Mr. Putin’s blunder in Ukraine might even be a lucky break for the world at a time when Xi Jinping is seizing total power in China and is mouthing threats about Taiwan.

For now, the U.S. approach seems straightforward. Provide weapons to help Ukraine reclaim territory and defend its airspace. Make it clear to Ukraine’s leadership where our risk limits lie while keeping Mr. Putin in the dark about the same.

A last thought: If the war is still ongoing by the 2024 election, whether or not Donald Trump is the GOP candidate, expect the U.S. intelligence establishment for the third time in a row to play an oversized role in our presidential election, mostly for ill.