Irregular commanders, like Prigozhin, appear to be calling more of the shots in Ukraine, war experts say.
Yevgeny Prigozhin, the group's founder, and his fighters have routinely criticized Russia's top military officials over their handling of Russia's faltering war in Ukraine.
In threatening to do so, the two "likely effectively blackmailed" Russia's military command into giving resources to Wagner, the ISW said in a Monday assessment.
Graves of Russian Wagner mercenary group fighters are seen in a cemetery near the village of Bakinskaya in Krasnodar region, Russia, on January 22, 2023.
Meanwhile, Prigozhin marked the occasion by feuding with Russia's military leadership, attacking their ability to defend the country.