US intelligence officials were able to gather an extremely detailed and accurate picture of Wagner chief Yevgeny Prigozhin's plans leading up to his short-lived rebellion, including where and how Wagner was planning to advance, sources familiar with the matter told CNN.
But the intelligence was so closely held that it was shared only with select allies, including senior British officials, and not at the broader NATO level, these sources said.
It was not clear exactly when Prigozhin would act, the sources said. But he appears to have decided to move forward with his plan following a June 10 declaration by Russia's Ministry of Defense that all private military companies, including Wagner, would be forced to sign contracts with Russia's military beginning in July and essentially be absorbed by the Russian Ministry of Defense.
The intelligence was so secret that within the US, it was briefed only to the most senior administration officials as well as the Gang of Eight members of Congress, who have access to the most sensitive intelligence matters.
The secrecy surrounding the intelligence was why some senior European officials and even senior officials across the US government were caught off guard by Prigozhin's attack on Friday, and the speed with which Wagner forces marched into Rostov-on-Don and up toward Moscow into Saturday morning, the sources said.
"It was an extremely tight hold," said one person familiar with the intelligence.
Some NATO officials expressed frustration that the intelligence was not shared. But doing so would have risked compromising extremely sensitive sources and methods, sources explained. Ukrainian officials were not told about the intelligence in advance, either, officials said, due primarily to fears that conversations between US and Ukrainian officials might be intercepted by adversaries.
Biden spent the days after the rebellion fizzled out speaking with allies, including the leaders of France, Germany, the United Kingdom and Canada, as well as Ukrainian President Volodymyr Zelensky. During those conversations, he shared what information the US had about the rebellion, according to officials, in order to ensure the leaders had a better understanding of what was known to US intelligence.
'Hiding in plain sight'
Prigozhin's uprising did not come out of nowhere. US officials had been tracking his ongoing growing feud with Russia's Ministry of Defense for months, and took note when threats were traded back and forth between them. There were also signs that Wagner was stockpiling weapons and ammunition leading up to the rebellion, CNN has reported.
Democratic Sen. Mark Warner of Virginia, the chairman of the Senate Intelligence Committee and a member of the Gang of Eight, said that Prigozhin's rebellion "was almost hiding in plain sight."
Still, it was surprising to US intelligence officials how little resistance Wagner faced.
"Putin of ten years ago would have never allowed this to play out the way it did," Warner said on CNN's "Inside Politics," adding that Putin is "clearly weakened."
"The fact that you have a mercenary group, that I don't think had a full 25,000 troops the way Prigozhin claimed, but was able to literally march into Rostov, a city of a million people which was the command and control for the whole Ukrainian war, and take it over with barely a shot fired -- that is unprecedented, to say the least," Warner said.
Multiple sources told CNN that US and Western officials believe that Putin was simply caught off guard by Prigozhin's actions and did not have time to array his forces against the Wagner mercenaries before they managed to seize control of the military headquarters in Rostov. Putin also likely did not want to divert significant resources away from Ukraine, officials said.
Officials do believe, however, that had Prigozhin tried to seize Moscow or the Kremlin, he would have lost -- decisively. That is likely why Prigozhin agreed to strike a deal with Belarus and ultimately turned his troops around, the officials said.
One former administration official told CNN that while there was "constant stress and tension between Prigozhin and the [Russian Ministry of Defense], there were moments when the US would not have been surprised if it spilled over into violent -- but localized -- skirmishes." But something on this scale was not something US intelligence had anticipated prior to a few weeks ago.
Biden said Monday he instructed members of his national security team to prepare for a "number of scenarios" as the mutiny was unfolding. The White House later declined to expand on what scenarios were explored, but people familiar with the matter said a wide array of contingencies were explored, including the possibility that Prigozhin could reach Moscow.
Once Prigozhin launched his rebellion, senior US officials began scrambling to connect with allies and partners and reiterate a key message: that the West should remain silent and not give Putin any opening to lay the blame on the US or NATO for the insurrection.
Privately, US officials were reinforcing to the Russian government that the US had nothing to do with the uprising -- and urging them to maintain the safety and security of their nuclear arsenal, officials said.
'Don't rock the boat'
On Saturday, before Prigozhin stood down, there was outreach to Ukrainian officials from allies on a number of different levels, cautioning them to resist taking advantage of the chaos to strike inside Russia, according to a Western official.
The concern was that Ukraine and the West would be seen as helping Prigozhin and threatening Russian sovereignty.
"The message was don't rock the boat here," the official said, adding that the message was transmitted at the foreign minister level, deputies and through ambassadors.
"It's an internal Russian matter," the official said the Ukrainian officials were told, echoing what US and other Western officials have said publicly. "Ukrainians were being cautioned by allies to not to provoke the situation. Make hay of opportunities on Ukrainian territory but don't get drawn into internal matters or strike at offensive military assets inside of Russia."
In the war, Ukraine is suspected of carrying out a growing number of covert cross-border attacks and sabotage on Russian military facilities and even a drone strike on the Kremlin. Ukrainian forces have shelled the Russian Belgorod region, near the border between the countries.
"You just don't want to feed into the narrative that this was initiative by us," the official said. "It's what the Russians always wanted, proving that there are threats to Russian sovereignty."