One year ago this week, the U.S. launched the surge in Iraq. The goal was to crack down on a growing insurgency and to create enough "breathing space" for Iraq's fledgling government to advance.
There is much debate over whether that surge has worked and what lessons the U.S. military should take from the experience.
Lt. Col. John Nagl has spent a lot of time thinking about how the U.S. should deal with insurgents.
Nagl is an expert on counter-insurgency. He spent time in Iraq as an operations officer for a tank battalion in Anbar province and, back home, has been training soldiers to teach and support Afghan and Iraqi forces.
He's now retiring from the Army and moving to Washington, D.C., to work with a think tank called the Center for a New American Security.
Nagl talks with Michele Norris about lessons learned for counter-insurgency.
He says winning a war against an insurgency is possible — but it takes an unconventional war strategy.