US intelligence officials believed that Yevgeny Prigozhin, head of the Wagner paramilitary group, had been planning mutiny against Russia’s military leadership for some timebut it was unclear what the ultimate goal would be, CNN reports.

Intelligence officials briefed congressional leaders earlier this week on the Wagner group’s movements and gathering of equipment near Russia.

American and Western intelligence officials had indications that Prigozhin was preparing for such a move, among others by gathering weapons and ammunitionreports CNN.

An intelligence source said “everything happened very quickly” and it was hard to tell how serious Prigozhin was to threaten the Russian military and where he would take his troops.

Prigozhin had vowed on Friday to strike back against the Russian military leadership over an alleged attack on a Wagner military camp and claimed control of military facilities in two Russian cities. But by Saturday afternoon, he announced he was withdrawing his forces and halting the march on Moscow, hours after the start of an insurgency that posed the biggest threat to Russian President Vladimir Putin’s rule in decades.

As the situation developed, American and Western officials were monitoring the situation from a distancein order that to avoid accusations from Putin that could implicate the West in the escalating crisisaccording to CNN.

No change in Russia’s nuclear posture

Since Prigozhin started his rebellion, the US saw no change in Russia’s nuclear posture, two US officials told CNN. “We have seen no change in terms of Russian nuclear forces,” a State Department spokesman said, adding that the U.S. “has no reason to adjust our posture based on developments. We have long-standing, established channels of communication with Russia on nuclear issues.”

The US continued to monitor Russia’s nuclear posture throughout the war in Ukraine, Despite the fact that Russia earlier this year suspended its participation in the single permanent nuclear arms control treaty between Washington and Moscow. That means the two nations no longer share certain information required under the treaty, including updates on the status or location of objects subject to the treaty, such as missiles and launchers.