Yevgeny V. Prigozhin quietly profited from his personal ties to President Vladimir V. Putin of Russia, winning lucrative catering and construction contracts with the Russian government while building a mercenary force known as Wagner.
After throwing his fighters into Ukraine, their ranks swelled with prisoner recruits, Mr. Prigozhin emerged as a public power player, using social media to turn tough talk and brutality into his personal brand.
In a scorching video posted Friday on social media, Mr. Prigozhin threatened to pull his fighters next week out of Bakhmut, the embattled city where he has thrown thousands of convicts into the maw of Ukraine’s defenses, taking extraordinary casualties in a stubborn effort to wear down the other side.
Citing a lack of ammunition, Mr. Prigozhin delivered the ultimatum after walking among rows of bodies that he claimed were Wagner fighters killed in the battle for Bakhmut.
He called out Russia’s defense minister, Sergei K. Shoigu, and Gen. Valery V. Gerasimov, the chief of the military general staff, as responsible for their deaths.