The former head of the UK military has said no one had a "true understanding" of the political situation in Afghanistan which resulted in the Taliban’s return to power.
General Sir Nick Carter, speaking on BBC Radio 4's Today programme which he guest edited, described the chaotic scenes in August as people tried to flee the country as "shocking".
He said he believes it is "probably still true" that most Afghans would not support the Taliban regime.
General Carter, who was Chief of the Defence Staff until the end of November, said he needed to be upbeat in his public statements to avoid undermining the former government, led by Ashraf Ghani.
He also defended using former Afghan president Hamid Karzai's description of the Taliban as "country boys" who lived by a "code of honour".
He told the Today programme: "I think at the end of the day it comes down to politics, the local politics in Afghanistan, and I don't think there was ever a true understanding of the political dynamics on the ground and therefore the ability to be able to rationalise that."
The speed of the government's collapse resulted in a rushed evacuation from Kabul airport in late August. UK and coalition troops flew British and American nationals, and Afghan civilians eligible for relocation, out of the country to escape the Taliban’s advance.
"They were shocking moments for all of us," Gen Carter said.
"And of course, you think of so many people in times like that - you think of all of those who've committed their lives to the cause over the last 20 years, you think of the Afghan people, and of course you wonder how it ended like that.”
He said the West now needed to engage with the Taliban to help get aid to the Afghan population which is facing a humanitarian crisis.
"I also think it's important that we engage because we might be able to encourage them to govern in a different way. And the fact that they are governing in an utterly un-inclusive way, is something that we need to worry about," he said.