“We hope that Afghan security forces will be ready to take lead in all of Afghanistan sometime in 2013,” Panetta said. As the Afghans take charge of security around the country, the United States will end its lead combat role, he explained.

U.S. troops will still “engage in combat operations as necessary” through the end of 2014, Panetta clarified. But he provided a narrow list of examples where such a combat role would be appropriate after the transfer to Afghan leadership. These included self-defense, counter-terrorism missions by special operations forces and “in extremis” situations. U.S. troops could also see combat while assisting and advising the Afghan forces, a Pentagon spokesman explained later.

What this means is that the Obama administration is betting that its core strategy of gradually transferring security responsibility to a beefed-up Afghan army will work. And if it doesn’t, and the Afghans can’t handle the load? I didn’t hear Panetta say that the Pentagon would send in more U.S. troops to fill that gap. Quite the opposite: This is a mission with a clear timeline and endpoint, following Panetta’s comments this week.

Why did Panetta decide to speak candidly with journalists traveling on his plane (including this superannuated reporter)? The answer is that he planned to discuss the 2013 transition timetable with other NATO defense ministers who are meeting here, and he didn’t want a garbled version to leak. Also, he wanted to make clear that, in advocating that NATO end its lead combat role in 2013, he wasn’t acceding to pressure from France, which had earlier announced it would end any combat role next year.

The confusion came because Panetta didn’t specify, the first time around, that some U.S. combat operations would be possible, even after the handover of lead responsibility. And various U.S. and NATO officials, worried by stories that suggested the United States was suddenly pulling the plug, scrambled to say that the initial stories had it wrong. But they didn’t.

Another cause for confusion was that Panetta scooped the grand announcement that had been planned for NATO’s summit meeting in Chicago. Big announcements about ending wars (or, to be more precise, transferring the lead combat role) are supposed to be left to heads of state, who can then get the political credit for bringing home the troops. In this case, Panetta apparently decided it was important to get the word out sooner, rather than later.

Is the U.S. exit strategy feasible? The truth is that nobody will know until the transfer of security responsibility to the Afghan army and police across the country actually takes place, sometime late next year. So far, the transition process has gone reasonably well in the provinces where the Afghans have taken control.

U.S. commanders are upbeat, but we really don’t know how well the Afghan troops will perform against a Taliban adversary that, although battered, remains a potent force. Perhaps more importantly, we don’t know if the corrupt and inefficient Afghan government can hold together when it’s floated free from the mother ship. Journalists will have to explore those issues over the next year, as the transition date comes closer.

One thing that’s clear from my many trips to Afghanistan over the past few years is that the Afghans perform better when they are mentored in the field by NATO partners. That means, for the transition process to have any chance to succeed, the United States and its allies will have to maintain a potent military presence until mid-2013, so that there’s a solid handoff. Otherwise, the air will rush out of this balloon, and instead of an Afghan lead, we’ll see a collapse.