Afghanistan: How the Taliban gained ground so quickly

The speed of the Taliban advance in Afghanistan appears to have taken many by surprise - regional capitals seem to be falling like dominoes.

The momentum is clearly with the insurgents, while the Afghan government struggles to keep its grip on power.

This week, one leaked US intelligence report estimated that Kabul could come under attack within weeks, and the government could collapse within 90 days.

So how did it unravel so quickly?

The US and its Nato allies - including the UK - have spent the best part of the last 20 years training and equipping the Afghan security forces.

Countless American and British generals have claimed to have created a more powerful and capable Afghan army. Promises that today appear pretty empty.