KABUL, Afghanistan – General David Petraeus isn’t planning to wake up one morning after July 2011 and order his troops out of Afghanistan’s provinces all at once. Instead, his idea is to slowly and deliberately remove small units, district by district, in an intricate process he describes as “thinning out.”

“You can reduce your forces. But you thin out,” Petraeus tells Danger Room in an interview from his professorial Kabul office. “You don’t just hand over. The whole unit doesn’t leave.”

At least not in the early stages after the Obama administration’s announced date to start a withdrawal. And some of those troops won’t come home right away: They’ll be “reinvested” at first in parts of the country where security remains dicey.

For months, Petraeus has been questioned about how quickly the U.S. will remove its troops from Afghanistan after July 2011. He’s heard lawmakers and pundits parse everything he says for the tiniest iota’s worth of difference with President Obama. It’s “premature” to speculate what will happen eleven months from now, Petraeus says. Once again, he declares support for the Obama policy of beginning a “conditions-based” drawdown next summer.

But for perhaps the first time, Petraeus opens up, just a bit, about his thinking for how to send troops home, and in what size.

A few combat brigades of between 3,000 and 5,000 troops, like those Obama ordered to Afghanistan last winter, may indeed come back to America. But he is maintaining the mantra that withdrawals next year, beyond the 30,000 surge troops, will depend on how the security picture looks. Petraeus says the recommendations will come from “those who know it best” — his subordinate commanders.