A NATO force was sent to Afghanistan 13 years ago to seek out al-Qaeda and destroy it. At its peak NATO's International Security Assistance Force (ISAF) numbered 140,000, with soldiers drawn from 46 countries.

I think as you look around, what the ISAF and what the coalition has done over the last 13 years is to provide hope to the Afghan people and as we move into resolute support that mission continues to change and it will over time.

General Campbell, commander of the International Security Assistance Forces

Their mission evolved. With al-Qaeda disappearing into the shadows ISAF took on the Taliban, who had hosted al-Qaeda leaders and their training camps before the 9/11 attacks.

The cost of this war has been far reaching. Almost 3,500 coalition soldiers have died and over 18,000 civilians were killed. In monetary terms the total in military and reconstruction budget runs into hundreds of billions of dollars.

A presidential election earlier this year, heralded as a sign of stability, and saw President Hamid Karzai hand power to Ashraf Ghani. President Ghani's first major act was to sign the BSA, the Bilateral Security Agreement, that permits 12,000 US soldiers to stay after 2014.

Al Jazeera went to Kabul to talk to General John Campbell who is tasked with finishing the job NATO started 13 years ago. He oversees the drawdown and is the last in a long line of commanding officers to navigate his way through the politics, violence and bloodshed of the Afghan conflict.

Campbell says of the human cost: "The Afghan people understand that sacrifice. They come up to me and say 'Thank you for the sacrifice , we know you have lost men and womem over years'. My message for the men and women of all of the countries who have lost loved ones here is that their sacrifice has not been in vain. They will see that Afghans understand that."

So, are Afghanistan's security forces ready to fill the vacuum that ISAF will leave behind? Are they equipped to stop a resurgence of the Taliban? And is al-Qaeda now eradicated once and for all?