Could The Afghanistan Deployment Happen Today?
In July, US President Joe Biden said the American mission would finish on 31 August - nearly 20 years on from when military forces first deployed to the country.
Since that announcement, however, violence in the country has been on the rise.
President Biden says he has no regrets over the decision to withdraw the US military from Afghanistan - but could the deployment to the country ever happen again?
Professor Malcolm Chalmers, Deputy Director-General at RUSI, told Forces News if the UK deployed "as part of a US-led coalition, we could deploy an effort comparable to the forces that went in 2001".
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But Prof Chalmers added that the 2006 deployment of British troops to Helmand was "quickly found" to be "not big enough".
"We had to ramp it up and really, we never got to a point of stability in Helmand until the Americans also joined us and we ended up with a force of, getting on for, 30,000 alliance troops in Helmand," he said.
"Having a one off deployment of 10,000 British troops to southern Afghanistan, you could do that, the challenge would be sustaining it over a long period of time.
"That was the challenge then, it would be the big challenge now."
Prof Chalmers also said that "if we knew then what we know now… we would've concluded it was the wrong thing to do to deploy to southern Afghanistan."