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Britain's chief of general staff says Russia has been "hammered" in its invasion of Ukraine and has warned that the conflict highlights the need for the UK to invest in more field forces.
General Sir Mark Carleton-Smith, the outgoing head of the army, said the land warfare taking place in Ukraine warrants a rethink on the cuts being made to the British Army.
It comes as defence secretary, Ben Wallace, announced the army would shrink by 10,000 troops by 2025, reducing it to its smallest size since the Napoleonic era, following a review last year.
Speaking at a webinar hosted by think-tank the Policy Exchange, Sir Mark said Russia was an "acute" threat and the defence review should be re-examined.
"I would like to see greater investment in a larger army," he said.
“I think our structure and the growing shopping list of potential outputs in the wake of the redefinition of European defence and deterrence, which I am sure Ukraine heralds, I think is going to demand more of the field force.
“The figure that came out of the review of 72,500 — subsequently amended to 73,000 — was not one that was predicated on most of the experimentation and analysis that underpinned the army’s proposition and contribution to the review."
He was joined by his US counterpart, General James C McConville, who said lessons need to be learnt looking at the land warfare taking place in Ukraine.
"I think what we are learning is the impact of strong allies and partners when you take a look at the land warfare taking place in Ukraine right now," Gen McConville said.
"Will is really important and we are seeing that unfold in Ukraine right now."
He said Russia's President Putin had unleashed a "complex" invasion plan - which would have taken the very best leaders and soldiers to execute it - which did not go to plan.
Sir Mark said he had been "surprised" at Russia's performance and said it had been "hammered".
He said he thought Russia would have learnt lessons from its conflict in Syria but instead "it went all in".
"In terms of execution, it was very poor," he said.
"Their commanders have struggled to administer and resupply their forces and there was a lack of low level initiatives, so when Plan A became unstuck it took sometime to reconfigure themselves, so we are 48 days into a war they thought would take five days.
"I think they are taking a hammering. It is difficult to know how many Russian casualties there have been but between 10,000 to 15,000 clearly in the first six weeks which is more than they suffered through the duration of the Afghan conflict. It is estimated between 20,000 to 30,000 wounded, these are very significant numbers."
He said Russia is taking a pause ahead of a renewed offensive in the south-east of Ukraine.