It remains unclear how low the number of U.S. forces will fall by the planned drawdown in 2014. Marine Gen. John Allen, the top allied commander, provided Defense Secretary Leon Panetta with three options: 6,000, 10,000, and 20,000 troops, according to The New York Times.
Experts tell U.S. News that middle number could provide the sweet spot the U.S. needs to demonstrate its troop withdrawal while still maintaining a force strong enough to prop up burgeoning Afghan security.
"Nobody is under the illusion ANSF will be completely independent and out on their own after 2014," says Dressler. "That was never the plan. That was never how things were conceived."
The residual force ought to be calculated based on certain key questions, he says, such as "What is the mission you're asking these forces to do and how many troops does it take to do it?" The White House and Pentagon should reevaluate the mission if the number of troops they deploy falls short of that requirement, Dressler says.
He predicts any significant drop in troop numbers will take place after the fighting season in the summer and early fall. Marine Gen. Joe Dunford will take command of ISAF in the coming weeks and will likely push for a continuation of troop levels.
"It would be unusual for a general to come in, be in control of a theater-level mission, and not have a say in the size and scope of the withdrawal he's going to have to carry out," says Dressler. "I don't see the rush, quite frankly. The Afghans still need a considerable amount of help, and we still have a considerable training mission underway."
Other experts believe political pressure might hasten lower troop levels much sooner.
Dunford and President Barack Obama will face stiff opposition from a Congress eager to bring combat troops home, says Bensahel.
"I suspect it will be a relatively steep drawdown through 2013, and see a force more like a post-drawdown 2014," she says.
PASSING THE TORCH
Allied forces started turning over security control of 87 percent of the country, according to an ISAF release on New Year's Eve. Allen congratulated Afghan President Hamid Karzai for accomplishing this, the fourth of five steps in the country's security transition.
"President Karzai's announcement of the fourth group of provinces to enter Transition is another historic step for Afghanistan as it gets closer to taking full responsibility for security of the entire country," Allen said in the Dec. 31 statement.
These five steps, or tranches, follow a process established at the Lisbon Summit in 2010 to turn over specific regions of the country to Afghan control. ISAF maintains these do not adhere to a specific timeline, but are based upon "operational, political, and economic considerations" from allied and Afghan assessments.
This transition began on March 22, 2011 for Kabul and two other regions in the eastern portion of the country. Karzai announced Tranche 2 in November 2011, followed by Tranche 3 in May 2012.
But this does not necessarily usher in an end to the fighting.
"If you forecast out...what you have to anticipate is an ongoing war," says O'Hanlon. "The idea that we've broken the back of the insurgency is unrealistic."