Fort Riley ? A mission that has trained more than 15,000 soldiers, sailors and airmen to be advisers in Afghanistan and Iraq is leaving Kansas after three years, shifting focus as it moves to Louisiana.

Instead of training teams of 12 to 16 people, the mission to be based at Fort Polk, La. will turn combat brigades of 3,500 soldiers into a brigade focused on advising. The change is part of the next phase in Iraq aimed at the withdrawal of troops in 2011.

The shift reflects not only a change in location for the training, but a change in the adviser mission.

Instead of training small groups and sending them to work as liaisons between U.S. forces and Iraqi forces, the teams will be brigade-sized and do much the same task. The idea is that with larger groups, the brigades can do a better job of training the Iraqis as the U.S. pulls back from combat operations.

Defense analyst John Nagl, president of the Center for New American Security in Washington, said the new system was a move in the right direction, giving brigades additional skills without compromising their combat abilities.

“We are figuring this thing out. This is a learning process,” said Nagl, a former Army colonel who trained advisers at Fort Riley and helped write the Army’s counterinsurgency manual.

He said the new brigades will have the ability to deploy repeatedly without needing to rebuild adviser units, saving time and resources.

The first brigades are being trained and deployed to Iraq, including three brigades of the 3rd Infantry Division from Fort Stewart, Ga., and one from 4th Infantry at Fort Benning.

About 90 percent of what U.S. forces are doing in Iraq is advising army and police forces to develop skills, said Col. Mark Bertolini, commander of the Fort Polk unit responsible for adviser training. That part of the mission will also grow in Afghanistan as that nation increases the size of its security forces.

Bertolini said brigades of advisers with good language and culture skills will enable the development of those forces.