Admiral Sir Tony Radakin, who heads up the British armed forces, told PA Media in an interview published Friday that the Russian president had used 25% of his country’s army but achieved only “tiny” gains.

“This is a dreadful mistake by Russia,” he said. “Russia will never take control of Ukraine. Russia has strategically lost already.”

Radakin explained that Moscow had been forced to abandon its objectives of seizing control of most Ukrainian cities, noting that Russian forces were vulnerable because they were running out of people and military hardware.

“Any notion that this is a success for Russia is nonsense. Russia is failing,” he told PA.

“It might be getting some tactical successes over the last few weeks, and those might continue for the next few weeks—but Russia is losing strategically.”

Spokespersons for the Ukrainian and Russian governments were not immediately available for comment when contacted by Fortune.

‘A disaster for Putin’

Chris Tuck, a reader in strategic studies at King’s College London, told Fortune that although Russian forces were having some tactical successes in limited areas, such as the eastern city of Severodonetsk, strategically the invasion of Ukraine has been “a disaster for Putin and Russia.”

Radakin’s comments, he said, were intended to separate Moscow’s limited successes from the bigger picture of what had been happening in Ukraine.

“Russia has categorically failed to achieve any of the objectives it set out to achieve in the initial stage of the invasion,” Tuck said in a phone call on Friday. “It obviously intended to try and regain control of Ukraine, and of course that hasn’t happened—if anything it’s pushed Ukraine further away.”

He noted that many of Moscow’s other objectives—like the weakening of NATO and the demonstration of Russia’s military power—had also been counterproductive.

One of Russia’s key demands as it amassed thousands of troops at the border it shares with Ukraine before invading its neighbor was that Ukraine should never be permitted to join NATO, the world’s most powerful military alliance.

NATO and the U.S. both said that such a request could not be accommodated, and since the invasion of Ukraine in late February, the alliance has stepped up its presence in eastern Europe while both Sweden and Finland have taken steps to join the organization.

Jonathan Eyal, associate director of strategic research partnerships at defense think tank the Royal United Services Institute, told Fortune on Friday that ultimately, Putin’s strategic objective in Ukraine was to re-create the old Soviet Empire by reimposing control over Ukraine.

“Russia has lost strategically if we assume, as looks likely, that the objective of Putin was to take over Ukraine and transform it into a satellite state under Russian influence,” he said. “So in that respect, Russia has failed strategically. It is now blatantly obvious that Ukraine may not regain full control of all its territory, but it will remain an independent state, and more importantly it will remain a state that will challenge Russian influence in the region.”

However, Eyal added that while it was true that the strategic objective of Russia had failed for the moment, this was merely a snapshot of the situation.

“The final judgment on this sad objective of Putin is yet to be delivered,” he told Fortune.

“The more important question still remains around what lesson Russian leaders draw out of the conflict. The debate is not really on whether Putin has failed strategically, but on whether it would be obvious to Russian decision-makers in the future that this was a disaster.”

Eyal also warned that if Putin succeeds in “grabbing a chunk of Ukraine” and the West remains divided on the country’s future, Russia could still achieve some of its long-term strategic objectives.

“Clearly Putin’s failed, but he may be able to snatch victory out of defeat if we [in the West] do not come to a very decisive conclusion what is going to happen to Ukraine after the fighting is over,” he said. “If Ukraine remains suspended in the air and nobody knows what to do with it, then Russia’s still got a chance to come back at it.”