Russia’s efforts to strengthen its military control over the Donbas region of eastern Ukraine failed, British defense experts said Saturday in their latest intelligence assessment released today.

The chief of staff of the Russian army Valery Gerasimov, who took over as head of the country’s so-called “special military operation” in Ukraine on January 11, sought to “launch a general winter offensive to extend Russian control over the entire Donbass region,” Britain’s Ministry of Defense said on Twitter.

“Eighty days later, it is increasingly clear that this plan has failed,” the text added.

At several points along the front, “Russian forces made only marginal gains, at the cost of tens of thousands of casualties,” the ministry said. This had the effect of “largely losing” the advantage in the number of military personnel which had been obtained by the partial conscription last year.

“There is a realistic possibility that Gerasimov is pushing the limits of how far Russia’s political leadership will be able to withstand failure,” the ministry estimates.

Britain’s Ministry of Defense has been providing daily intelligence updates to its agencies since Russia’s invasion of Ukraine began. Moscow accuses London of a targeted disinformation campaign.