Wagner Group
Sergei Surovikin has a "long association" with the mercenary group which challenged Vladimir Putin.
The next challenge for the US, Jon Huntsman said, will be to prepare for a post-Putin Russia.
"I'm not sure why Putin bothered to put this out," one person tweeted.
Wagner Group mercenaries advanced toward Moscow before an agreement to stop the mutiny and send their chief to Belarus.
The Russian state is facing its "most significant challenge" in years, according to the Ministry of Defence.
UK intelligence says it's a blow for Moscow as it tries to deal with Ukrainian counteroffensive.
Yevgeny Prigozhin's statement defied the Russian president's orders.
Yevgeny Prigozhin said Russia's military had failed in Ukraine.
This is causing deep divisions within the Kremlin's chain of command, according to British intelligence.
Privately-employed troops are "less constrained by the limited pay levels and inefficiency which hamper the effectiveness of the regular army".