A few combat brigades of between 3000 and 5000 troops, like those Obama ordered to Afghanistan last winter, may indeed come back to America. But in keeping with the mantra – articulated by both Petraeus and, yes, the president – that withdrawals next year beyond the 30,000 troops of the surge will depend on how the security picture looks, Petraeus says that the recommendations will come from “those who know it best”: his subordinate commanders. They’ll assess how much sense it makes to move troops out of certain areas; whether there’s more that troops still need to achieve in battle; and whether Afghan troops and police are ready to hold terrain that Americans cleared. Much as Obama will consider Petraeus’ advice, Petraeus will consider theirs.

That focus will “start at the district,” he says, and then progress to the larger provinces. The idea is to ensure that U.S. troops don’t vacate a hard-captured area and abruptly turn it over to unprepared Afghans. “We’ve got a lot of months in this fighting season and a lot of work to do before July 2011,” he adds. “But in the tough areas, it’ll probably be district-level. More autonomous areas, it can be province-level.” (Brigade-sized Task Forces typically handle security in more than one Afghan province.)

Some units pulled out of stable districts might find themselves heading for more volatile ones. “You maybe take one company and send it somewhere else. Maybe send it home,” Petraeus explains. “We want to reinvest some of the transition.” It won’t necessarily be the case that a unit that “thins out” from a district heads directly home. “Some will, certainly,” Petraeus qualifies. “And this is all premature.”