The information was considered both solid and alarming because of the possibility that a major nuclear-armed rival of the United States could descend into chaos.
American intelligence officials briefed senior military and administration officials on Wednesday that Yevgeny Prigozhin, the leader of the mercenary Wagner Group, was preparing to take military action against senior Russian defense officials, according to officials familiar with the matter.
U.S. spy agencies had indications days earlier that Mr. Prigozhin was planning something and worked to refine that material into a finished assessment, officials said.
The information shows that the United States was aware of impending events in Russia, similar to how intelligence agencies had warned in late 2021 that Vladimir V. Putin was planning to invade Ukraine.
But unlike with the initial invasion, when U.S. officials declassified the intelligence and then released it to try to deter Mr. Putin from invading, intelligence agencies kept silent about Mr. Prigozhin’s plans. U.S. officials felt that if they said anything, Mr. Putin could accuse them of orchestrating a coup. And they clearly had little interest in helping Mr. Putin avoid a major, embarrassing fracturing of his support.
In this case, the information that the long-running feud between Mr. Prigozhin, who got his start as “Putin’s chef” in St. Petersburg, and Russian defense officials was about to devolve into conflict was considered both solid and alarming. Mr. Prigozhin is known for his brutality, and had he succeeded in ousting the officials, he would likely have been an unpredictable leader. And the possibility that a major nuclear-armed rival of the United States could descend into internal chaos carried with it a new set of risks.
While it is not clear exactly when the United States first learned of the plot, intelligence officials conducted briefings on Wednesday with administration and defense officials. On Thursday, as additional confirmation of the plot came in, intelligence officials informed a narrow group of congressional leaders, according to officials familiar with the briefings who spoke on condition of anonymity because they were not authorized to speak publicly. By Friday night, Mr. Prigozhin had dramatically escalated his feud, launching a march on Moscow that the Russian government described as an attempted coup. On Saturday, he called his fighters off and agreed to flee to Belarus.
CNN earlier reported that the United States had briefed congressional leaders about their concerns that Mr. Prigozhin was preparing to challenge Russia’s military leadership.
For years, Mr. Prigozhin hated Sergei K. Shoigu, the minister of defense, and Gen. Valery Gerasimov, the chief of the general staff of the Russian armed forces, and the feeling was mutual, U.S. officials said. But it took the war in Ukraine, officials said earlier this year, for the animosity to spill into the open, frequently expressed by Mr. Prigozhin in ill-tempered posts on Telegram, a social media platform.
In recent months, intelligence officials have tracked the growing animosity between Mr. Prigozhin and leaders of Russia’s defense ministry and spent considerable time analyzing it.
The intelligence agencies’ conclusion was that it was a clear sign of the internal tensions caused by the war in Ukraine, a product of Russia’s struggle to supply its troops adequately.
It was an indication, one official said, of how the war was going badly for both Wagner and the regular military.
Intelligence reports released as part of the Discord leaks also showed that the United States had intercepted communications between senior Russian military leaders debating how to handle Mr. Prigozhin’s constant demands for more ammunition.
In interviews before the current crisis, U.S. officials said it was not just Wagner forces that faced supply shortages, but the entire Russian military. Those problems have plagued the Russian military for months, but American officials said earlier this week that they had become more obvious as the Ukrainian counteroffensive began.
Mr. Putin also may have given Mr. Prigozhin the false belief he could move beyond public criticism to action against his military allies. During the fight for the city of Bakhmut, the U.S. government assessed that Mr. Putin very likely ordered regular Russian units to reinforce Wagner forces.
After the capture of Bakhmut, the Russian defense ministry moved to cut down the power of Wagner. Russia forced all volunteers for its forces to sign contracts with the Ministry of Defense. The move cut Wagner off from recruits and meant that for the mercenaries to return to the battlefield in Ukraine, Mr. Prigozhin would have to subordinate his forces to the Defense Ministry, said Tatiana Stanovaya, a senior fellow at the Carnegie Endowment for International Peace.
Placing Wagner forces under the control of Mr. Shoigu was “out of the question” for Mr. Prigozhin, Ms. Stanovaya said.
Many of Mr. Prigozhin’s tensions with the military had played out in public. He used interviews and Telegram posts to berate Mr. Shoigu and General Gerasimov, calling them incompetent and charging that they were misleading Mr. Putin about the progress of the war with Ukraine.
American officials conceded that there was an element of theater to Mr. Prigozhin’s public complaints but that it was nevertheless useful for Mr. Putin, who himself has privately criticized his military leadership for being too passive during the Ukraine war.
Still, American officials concluded that Mr. Prigozhin’s public statements were not controlled by Mr. Putin. His fight with the ministry of defense, officials said earlier this year, was real, not political theater, fueled by the huge casualties Russia had suffered in Bakhmut.
Mr. Prigozhin’s critique went beyond an argument over needed supplies. He charged that the military leadership was corrupt and incompetent. For their part, some military leaders were jealous of his influence with Mr. Putin, American officials said earlier this year.
But it was only in recent days that intelligence officials got the initial warnings that Mr. Prigozhin might take action.
Officials said that intelligence agencies had not known what the results of Mr. Prigozhin’s actions might be, but they were immediately worried about how it might affect the control of Russia’s nuclear weapons. President Biden, speaking in October, talked of the dangers that Mr. Putin would pose if he felt cornered and said the United States was looking for “off ramps” for Mr. Putin.
Since Mr. Prigozhin took action on Friday, American officials have been locked down, saying little publicly about his intentions or what they knew about events on the ground. Officials have been wary, both because events were moving fast and because they did not want to give Mr. Putin any excuse to blame the West for Mr. Prigozhin’s actions. But several officials said they fully expected that Mr. Putin would eventually say the uprising was the result of a foreign plot.
Mr. Prigozhin is under indictment in the United States for his role in trying to influence the 2016 presidential election in favor of Donald J. Trump.
David E. Sanger is a White House and national security correspondent. In a 38-year reporting career for The Times, he has been on three teams that have won Pulitzer Prizes, most recently in 2017 for international reporting. His newest book is “The Perfect Weapon: War, Sabotage and Fear in the Cyber Age.” @SangerNYT • Facebook
Julian E. Barnes is a national security reporter based in Washington, covering the intelligence agencies. Before joining The Times in 2018, he wrote about security matters for The Wall Street Journal. @julianbarnes • Facebook
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