“Victory for the Ukrainians is coming very fast,” says Bernard-Henri Lévy. “And I was the first to predict it.” Mr. Lévy is on his fifth visit to the country since Vladimir Putin launched his invasion in late February; his first was in mid-March.

“I am in the east,” he tells me Wednesday by WhatsApp, the least unreliable way to communicate from the front lines. He’s in Kupyansk, a town “just liberated,” then to Izium, where “Ukrainian families are just beginning to return.” Two days earlier, the Russians had bombed the heart of Ukraine’s capital, Kyiv, including a children’s playground. But he still feels “a strong wind of victory. A sad victory, of course. A victory in the midst of graves, but victory nonetheless.”

Mr. Lévy, 73, is conventionally billed as a “French philosopher.” That’s wholly inadequate to describe a man who’s also a journalist and filmmaker, a passionate crusader for democratic rights, and a freelance envoy of the Western world to war zones on almost every continent. We met last month, after his return from his fourth Ukraine visit, in Mr. Lévy’s exquisitely furnished and commodious apartment in the heart of Paris.

He leads a magnificent life and has no need to risk his neck in Ukraine or elsewhere. Yet he does. He is a wealthy man—heir to his father’s timber fortune and the author of several best-selling books—and he often pays his own way to these combat zones, setting himself the task of highlighting the plight and the needs of the people at war. “I have the means,” he says, “and the time.” He also feels “a duty, as an intellectual whose voice is heard, to ring the bell and warn the world.” He confesses to a kinship with the Ukrainian people. Ever since he visited Kyiv during Ukraine’s democratic Maidan Revolution in 2014, he’s regarded them as “the sentinels of the West,” on the front line with Russia.

We meet days after the Ukrainian armed forces liberated Lyman, a town in the east that the Russians had captured and ravaged. We sit at Mr. Lévy’s dining table, a large map of Ukraine spread out between us. He’s “not at all surprised” by the victory in Lyman. “I was there with the Ukrainians, a few kilometers from the city, a few days before the offensive,” he says. “One could feel the encirclement of the Russian forces, just as one could feel the solidity of the Ukrainian positions. One could see how they were, little by little, transforming from defensive positions into offensive ones.”

Mr. Lévy speaks of the war with the authority of a man who has seen it up close—who has been in foxholes alongside troops as they exchanged fire with Russians. He has been pilloried for this on Twitter by half-wits who dwell not on the great risks he runs to report on the war firsthand, but on the suit he wears under his flak jacket.

He says he dresses up for the battlefield for the same reason he does when he meets “a senator in D.C., a friend in New York, or my publisher in Paris”: “Few deserve more respect than those who risk their lives, buried in trenches, to defend our shared values.” He also wears a suit for our interview, late on a Friday evening. No one is around but us and his impeccable Sri Lankan butler, who has worked for Mr. Lévy for 32 years and still doesn’t speak a word of French.

The Ukrainian soldiers on the front, Mr. Lévy says, had “a sense of calm, a strength, and a steel morale.” Lyman was a “key hub for the Russians in the region. And they lost it. Their entire infrastructure in the region will be weakened, and even if they try a counterattack, we’ll be able to see further pushes, even stronger still, by the Ukrainian forces.”

The Ukrainians have “a determined army which takes its time and tightens its grip little by little.” Their superiority to the Russians on the battlefield is apparent. “The Ukrainian generals are the better strategists, not the Russians,” he says. “But the real reason Putin has not succeeded”—the reason Ukrainian morale has remained high even in the face of the most “stomach-churning” Russian atrocities against civilians—is that “they know why they fight.”

They fight not only for “their existence, their survival,” but also for “values which they believe are worth risking their lives for,” Mr. Lévy says. That’s what led him to conclude in March that the Ukrainians would win: “I said it very early on. And I never, absolutely never, doubted it.” Everyone around him was saying, “Putin will never accept this, the Kremlin will never accept that.” But Mr. Lévy has covered many wars, and he’s found “there’s a simple law”: The people, not only the generals, must embrace the fight. “It’s the poor civilians that are sent to face the machine guns and who, in an instant, accept or refuse to go. And in this situation, when you know why you are there—when you defend your city, your house, your children, and, even more important, a creed that is deep within you—you go.”

The Russians offer a vivid contrast: “When you don’t understand what you’re doing there, when you don’t know why you are fighting, when you understand that you were sent to your death to satisfy the whims of a crazy, belligerent tyrant—well then, no one, no Putin in the world, can push you to step up to fight.” It won’t be long, he forecasts, before “the Russian army will really collapse from inside.”

Already Mr. Putin has had to resort to conscription. Mr. Lévy invokes the “era of Soviet dissidents, like in Solzhenitsyn’s books, with men breaking their own arms not to be enlisted in the army.” When people are at this point, “I don’t see how you can build a real army. The dictator has to resort to calling for mercenaries, for gangsters taken out of jail, for hysterical Chechen Islamist militants, and for the blind shelling of cities.” When a dictator is “reduced to that, I don’t see how he can win.”

In his visits to Ukraine, Mr. Lévy has seen proof of the barbarism of the Russians, “who are weak in front of the strong and strong in front of the weak.” He calls this the “definition of cowardice,” the opposite of the Ukrainians’ “nobility” and “sophistication.” Is Mr. Lévy romanticizing the Ukrainians? He says no: “For the moment, I don’t romanticize. I believe that there is, between Russia and Ukraine, a clash of civilizations.” There are no perfect states, he allows, “and when peace comes, I’m sure there will be a necessary democratic push to be made in Ukraine. But if Putin wins the war, it would be a serious weakening of the West and of America. Ukraine is the rendezvous, the call to arms, of our times.”

America’s strength obsesses Mr. Lévy, who may be France’s most pro-American public figure. “Anti-Americanism,” he says, “is one of the very significant and dark benchmarks of the worst instinct in France, which is often fascism.” He describes Mr. Putin as “authentically a fascist” for whom “America is the devil and the West the embodiment of decay.” Western values are “what he attacks through the pretext of Ukraine,” Mr. Lévy says. Ukraine’s “great virtue”—its embrace of European and Western values, and of America—was “impossible for Putin to digest.” It is what drove him to rage, and to war.

Western public opinion on Ukraine has been more favorable than he expected: “I’m always surprised when the worst does not happen.” He expected trouble, “especially in America, which is in the middle of a political mess where you have the America-first people on one side—the Trumpers—and the woke people on the other, some of whom say that this is just a war between white people, so it’s not our affair.” In Europe, there’s “the Munich tradition, which runs really deep.” The first reflex on the Continent “is often the worst. ‘OK,’ they say, ‘we are not going to enter into this mess. We are going to appease.’ Appeasement!”

But stiffened by widespread public support for Ukraine, politicians on both sides of the Atlantic have thrown their weight behind the Ukrainian people and government. Mr. Lévy has special praise for former British Prime Minister Boris Johnson and French President Emmanuel Macron. The latter “said from the very beginning that he wanted Ukraine to win. He said from the very beginning that the only ‘political solution’ is a military victory for Ukraine.”

He also esteems President Biden, at least when it comes to Ukraine. “The Joe Biden era is not the Barack Obama era,” Mr. Lévy says. Mr. Biden, “one of the architects of the Obama strategy that weakened America in the eyes of the world,” has undergone “a sort of secular miracle.”

Mr. Putin had been “watching America retreat” from theater after theater. Mr. Obama failed to “impose any consequences” on the Russia-backed Syrian regime after it crossed Mr. Obama’s “red line” and used chemical weapons on its own citizens in 2013. Donald Trump abandoned the Iraqi Kurds in 2017 and the Syrian Kurds in 2019, after which they were assaulted by pro-Iranian militias and the Turks, respectively. And then there was the “shameful, absurd” retreat from Afghanistan in 2021.

“Put yourself for one minute in the head of Putin,” Mr. Lévy says. “When you see these repeated retreats by America, when you see America betraying its allies and friends, you say, ‘OK, I have a green light. Yeah, I’m green-lighted to go into Ukraine.’ ”

Mr. Lévy is inclined to think that Mr. Biden’s toughness on Ukraine may also be a way to “make up for the self-inflicted Saigon” of the Kabul withdrawal. “I’m sure Ukraine is seen as a way to recover the spirit, the values, the greatness of America.” America “is back,” Mr. Lévy says, unironically echoing a Biden slogan from before the Afghanistan pullout. “It, and the West, has regained much of its credibility because the reply to Putin’s offensive has been strong and wise.”

The Russians should understand that “the Obama era—or the Obama-Trump era if you like—is closed.” Mr. Biden isn’t Mr. Obama: “He’s responding to war crimes with military help. He is a strong and unambiguous partisan on the side of the victims against the aggressor. He is, at the moment, faithful to some of the best American values.” Mr. Lévy has seen reverence—even love—for America on the Ukrainian front lines. He also saw “a desperation” on the part of the Ukrainians to prise themselves away from Russia forever and become a part of Europe.

How will we know that Ukraine has won? “It’s very simple,” Mr. Lévy says. “We’ll be able to celebrate victory on the day that Putin will capitulate. Not just lose, but capitulate. Bring back his army to where it was before this long war.” Putin must “evacuate his war dogs from the territories he claims absurdly to have ‘annexed,’ and also, of course, from Crimea.” Mr. Lévy is adamant there is no other solution that will afford a durable peace. “And no other solution, also, if we wish to end the energy, nuclear and even terrorist blackmail that the Kremlin has inflicted on us.”

He likens the present day to early 1945, when victory in World War II was approaching. “Did the democracies negotiate with Hitler? Did they look for compromises? Or offer him an exit ramp? No. They demanded his capitulation with no conditions. Well, it is the same with Putin.” The people of Ukraine don’t want to negotiate. They want justice, “not revenge.” And justice, Mr. Lévy says, “must be quick, must be fair, and must be severe.”

Mr. Varadarajan, a Journal contributor, is a fellow at the American Enterprise Institute and at New York University Law School’s Classical Liberal Institute.