Members of Wagner Group prepare to pull out from the headquarters of the Southern Military District to return to their base in Rostov-on-Don late on Saturday Wagner Group mercenaries withdraw from Russia’s Southern Military District HQ on Saturday after a peace deal was struck - Roman Romokhov/AFP via Getty Images

Russian intelligence services threatened to harm the families of Wagner leaders before Yevgeny Prigozhin called off his advance on Moscow, according to UK security sources.

It has also been assessed that the mercenary force had only 8,000 fighters rather than the 25,000 claimed and faced likely defeat in any attempt to take the Russian capital.

Vladimir Putin will now try to assimilate Wagner Group soldiers into the Russian military and take out its former leaders, according to insights shared with The Telegraph.

The analysis offers clues into the mystery of why Prigozhin, the Wagner Group leader, called off his mutinous march on Moscow on Saturday just hours before reaching the capital.

There remains speculation about what formal deal was struck, if any. The Kremlin said on Saturday that Prigozhin would head to Belarus in exchange for a pardon from charges of treason.

There has been no comment from Prigozhin over the suggestion. It also remains unclear if Sergei Shoigu, the Russian defence minister, is set to be demoted or fired, as Prigozhin demanded.

On Sunday, the Russian MP Andrey Gurulyov, a prominent Kremlin propagandist, said there was “no option” but for Prigozhin and another high-profile Wagner figure to be executed.

Putin has not been seen in public since addressing the nation on Saturday morning, but a pre-recorded interview filmed earlier in the week was played on state television on Sunday.

In the interview, Putin expressed confidence in realising plans for what he continues to call the “special military operation” in Ukraine.

Reports emerged that the United States was aware of a possible Wagner mutiny days before it happened, with The Washington Post quoting an official saying they knew “something was up”.

Figures in Washington, DC were said to have become concerned that Putin could lose control of his nuclear arsenal if a full coup was mounted against the Kremlin.

Russia’s ministry of defence said Ukraine used the chaos unleashed by Prigozhin’s coup attempt to step up its attacks around Bakhmut in Donbas. On Sunday, Ukraine’s military said that it had taken ground.

“Any chaos behind the enemy lines works in our interests,” said Ukrainian foreign minister, Dmytro Kuleba.

The British ministry of defence also said that Ukraine had increased its attacks over the past few days and had refined their tactics against “well prepared” Russian defences.

“Ukrainian units are making gradual but steady tactical progress in key areas,” it said in its morning intelligence briefing.

Ukraine launched its much-vaunted counteroffensive against Russia’s frontline around three weeks ago but had made slow progress.

Analysts have said that the distraction of Prigozhin’s coup attempt may have weakened Russia’s frontline.

The Kremlin didn’t withdraw any units to defend Moscow against Wagner fighters but Prigozhin called for regular army soldiers to desert. ‘So this raises profound questions’

On Sunday, Antony Blinken, the US Secretary of State, said that the armed uprising in Russia exposed “real cracks” in Putin’s authority after he was forced into an amnesty deal.

Mr Blinken told CBS News that the development marked “a direct challenge to Putin’s authority. So this raises profound questions, it shows real cracks”.

The impact of the Wagner mutiny on the battlefield in Ukraine remains to be seen. Ukraine said fresh gains in its counter-offensive had been made over the weekend.

The Kremlin has said that Wagner soldiers who did not take part in the coup will be taken into the Russian defence forces while claiming that those who did not will no longer be prosecuted.

Meanwhile, members of Russia’s convict army have issued threats against Prigozhin, claiming he betrayed them by abandoning the Kremlin coup attempt.

A video posted online by the prisoners-turned-fighters accused Prigozhin of “cowardice”, saying his supporters had been “double crossed” and now faced retribution.

One of the Storm-Z soldiers could be heard saying that Prigozhin had “promised everything” to them and then “turned the steering wheel in the other direction”.