Explainer: What remains as U.S. ends Afghan 'forever war'

Soldiers waiting on a tarmac.
American soldiers wait on the tarmac in Logar province, Afghanistan, Nov. 30, 2017. Starting Saturday, the last remaining 2,500 to 3,500 American troops will begin leaving, to be fully out by Sept. 11 at the latest.
Rahmat Gul | AP 2017