It's America's longest war. And in many ways it's most frustrating.
"When the Taliban were driven out of Kabul and Kandahar and their military forces were defeated, that would have been a very good time to leave," said Dr. Kalev Sepp, a professor at the Naval Postgraduate School in Monterey.
That happened more than a decade ago and we did not leave.
Dr. Sepp is a former green beret, and one of America's foremost experts in fighting an insurgency.
He says nation-building in Afghanistan once the major combat was done was difficult, bordering on the impossible.
"This isn't fixing a few roads and bridges and helping set up television stations," said Dr. Sepp. "This is, you know, you're talking about lifting a society where most people don't have access to electricity."
In Iraq, General David Petraeus and the generals who followed him ran a classic counterinsurgency campaign, supporting the government, protecting the populace, even paying insurgents to lay down their arms. It allowed coalition forces to cut the number of insurgent attacks and stabilize the government long enough for troops to pull out.
That's called continuity of leadership and it was not the way things worked in Afghanistan
"By my count right now, we've had 11 overall U.S. commanders in Afghanistan during 12 years of war," said retired U.S. Army Lt. General David Barno.
Barno would know something about that. He commanded coalition forces in Afghanistan from 2003 to 2005.
"No university and no business could survive that kind of turnover and remain successful," Barno said. "We're doing this in the middle of a war where the enemy is actively trying to make you fail."
U.S. forces have now taken up a support role, letting Afghan forces plan and conduct raids, find and defuse bombs, and provide security in the countryside.
Most American combat troops are supposed to be out of the country by the end of next year, leaving behind a small counter-terror force of several thousand soldiers.
But the Obama Administration is threatening to pull them out sooner because of erratic behavior by Afghan President Hamid Karzai.
And that could lead to this worst case scenario.
"One of the possible outcomes is having some kind of proxy civil war erupt in Afghanistan where the neighbors are using forces, whether it be the Taliban or other ethnic forces in Afghanistan, to fight each other," Barno said.
General Barno says that would be very bad for the United States. Best case scenario, he says a new president, a competent Afghan defense force, and maybe $10,000 U.S. troops to guard against a resurgence of al Qaeda.