The lesson we failed to learn from 9/11: peace is impossible if we don’t talk to our enemies | Jonathan Powell

We should have engaged with the Taliban 20 years ago, but we thought the winner takes all. It undermined our own armed forces

• Jonathan Powell was Tony Blair's chief of staff from 1995 to 2007

The fall of Kabul 20 years after 9/11 represents not just the failure of the western strategy in Afghanistan but a wider failure of our overall strategy in tackling the terrorism that gave rise to the attacks in New York and Washington.

There was no real alternative to going after the leadership of al-Qaida after the attacks that cost nearly 3,000 lives; and once the Taliban refused to hand over Osama bin Laden, there was no real alternative to taking on the Taliban themselves. That is why the invasion in support of the Northern Alliance enjoyed widespread support at the time around the world.