The several hundred American soldiers on this remote base in Afghanistan's wild east are the vanguard of a transformed U.S. military mission meant to avoid the kind of unraveling of security that happened this year in Iraq and ensure that the reason for invading Afghanistan in the first place — al-Qaida's haven for plotting the Sept. 11 attacks — never recurs.

These soldiers, including elements of the 3rd Infantry Division and the 3rd Cavalry Regiment, are not fighting the Taliban. They are trying to script the final chapter of the U.S. part in a conflict that seems certain to continue after the Americans leave.

Gamberi, a dusty outpost in Laghman province near the fabled city of Jalalabad, will be one of four "Train, Advise, Assist Commands" across the country, in addition to several training establishments in Kabul, the capital.

Gone are the days of large U.S. combat forces here or in any other part of Afghanistan, although U.S. special operations forces will continue, mostly in conjunction with Afghan forces, to hunt down al-Qaida remnants or other terrorists.

U.S. troops also will take on the Taliban in situations where they are deemed to pose a threat to American troop security.

The largest mission, however, is going to be training the Afghans — not on the front lines but at bases such as Gamberi.

U.S. Defense Secretary Chuck Hagel dropped in Sunday to get briefed on their work and to deliver a holiday-season pep talk.