Bakhmut has exposed an ugly, personal feud between the Russian Defense Ministry and ‘Putin’s chef.’

For nearly a year, Russia has waged a vicious battle to capture the Ukrainian city of Bakhmut, seeking a gain after months of embarrassing setbacks on the battlefield.

Although the city has been essentially razed, seizing it and ending the longest battle of the war would be a political, if Pyrrhic, victory for Yevgeny V. Prigozhin, the founder of the Wagner paramilitary group, whose mercenaries have led the assault on Bakhmut.

For Mr. Prigozhin, capturing the city appears to have become a personal obsession — so much so that one facet of the battle’s legacy will be the bizarre, public feud it set off between him, the man once known as “Putin’s chef,” and the Russian Defense Ministry.

Mr. Prigozhin is an oligarch who amassed his wealth partly through securing catering contracts from the Kremlin — hence the “chef” moniker. His notorious Wagner mercenary force has exerted influence on behalf of Moscow in Syria, Libya, the Central African Republic, Sudan, Mali and Mozambique, and it is now a crucial force fighting on Russia’s behalf in Ukraine — though Mr. Prigozhin publicly acknowledged his connection to Wagner only in September.

Since then, he has built an aggressive social media presence, portraying himself and his forces as more ruthless and effective fighters than the Russian military, and denouncing Moscow’s defense bureaucracy — all despite his close alliance with President Vladimir V. Putin.

Mr. Prigozhin’s pointed accusations about the competency of the Russian defense ministry, paired with his fighters’ advances in the grinding battle for Bakhmut, transformed him from a once-secretive figure into a political power player on the public stage.

The discord between Mr. Prigozhin and Russian defense officials was increasingly exposed as the anniversary of the war approached in February.

Back then, Mr. Prigozhin’s mercenary group was losing its ability to replenish its ranks. Sheer numbers of troops, some of whom Mr. Prigozhin recruited from prisons, had fueled Wagner’s repeated offensives in Bakhmut. But news of Wagner’s astronomical casualty rate was spreading to Russian penal colonies, and Mr. Prigozhin announced in early February that he would stop recruiting inmates, without giving a reason.

Not long afterward, he took aim at figures near the very top of Russia’s command structure, accusing the defense minister and the country’s most senior general of treason in vitriolic, profanity-laden audio messages on social media.

Mr. Prigozhin claimed that military officials were deliberately withholding ammunition and supplies from Wagner fighters in Bakhmut to undermine him, while, he said, Russian forces elsewhere faced failure after failure.

According to a classified U.S. intelligence document that was leaked online in April, the dispute grew so bad that Mr. Putin became personally involved, calling Mr. Prigozhin and Russia’s defense minister, Sergei K. Shoigu, into a meeting believed to have taken place on Feb. 22. “The meeting almost certainly concerned, at least in part, Prigozhin’s public accusations and resulting tension with Shoygu,” the document says, using an alternative transliteration of the minister’s name.

The public intensity of the dispute has since fluctuated. Mr. Prigozhin eventually said his fighters in Bakhmut received the ammunition they needed, and in April, Russia’s defense ministry made a rare acknowledgment of their cooperation, saying that Russian paratrooper units were covering Wagner’s flanks in the western part of the city.

But over the course of just three weeks in May, Mr. Prigozhin again accused Russia’s military bureaucracy of starving Wagner forces of the ammunition they needed to fully capture Bakhmut, this time threatening to withdraw them from the city on May 10; appeared to backtrack two days later, as he has done before, this time saying he had received satisfactory promises of more arms; undermined the Russian Army’s claims of a partial “regrouping” of its forces in the city by declaring it a “rout”; denied a report that he had offered to betray the Russian Army’s locations around Bakhmut if Kyiv agreed to withdraw from the area; and on Saturday, declared that Bakhmut was fully under Wagner control.

Kyiv swiftly denied the latest claim. In a reflection of how the public feud has exposed fault lines in the typically impenetrable world of the Russian military, Moscow has so far stayed silent.