President Obama vowed to keep to his exit strategy in Afghanistan, despite the recent tragedies, including the massacre of 16 civilians in Kandahar by what the military says was a lone gunman.

“It makes me more determined to make sure that we’re getting our troops home. It’s time,” he told KDKA television of Pittsburgh, one of a series of interviews with local stations he did at the White House.

“But what we don’t want to do is to do it in a way that is just a rush for the exits,” he stressed. “We’ve got to make sure that the Afghans can protect their borders and prevent Al-Qaeda from coming back, and so we’re going to have to do it in a responsible way.”

While this is the claim in public, it’s belied by the fact that a lot of Americans, including the reporter here, still believe that the timeline for withdrawal for US combat troops in Afghanistan has been set at the end of 2014. Jay Carney reaffirmed the timeline yesterday. But prior to the shooting spree, Leon Panetta had already agreed with his NATO partners to move up the end of the combat mission by a year, to 2013. And the Guardian (UK) reports that President Obama and Prime Minister David Cameron will secure that timeline today. It’s not dissimilar to how it worked in Iraq: the Afghans will now take the lead in the combat mission by the middle of 2013, a little over a year from now, and then full withdrawal of troops not affiliated with the training mission out by the end of 2014 at the latest.

(Cameron) will tell Obama that Britain remains in “lockstep” with the US on the plan to withdraw all combat troops from Afghanistan in 2014.

Last month, Leon Panetta, the US defence secretary, said US troops would “hopefully” just be involved in a “training, advice and assist role” by the latter half of 2013.

Britain asked for what is politely being described as an explanation and was reassured that the US remained committed to the timetable agreed by Nato leaders at a summit in Lisbon in 2010. Security in more than half of Afghanistan is led by the country’s own security forces. The aim is for the rest of the country to be handed over by 2013.

This wasn’t publicized enough at the time. But the plan is for no more NATO-led raids or combat missions within 16 months’ time. And the surge troops will leave the country by this September. So it’s fine to project steely determination, and call it “the good war” and all that, but we’re actually on our way out in Afghanistan.

My feeling is that it’s not that one tragic murder spree should lead to the end of combat operations. It’s that the murder spree was tragic, AND combat operations should end. There’s more than enough support for the contention that we have no business left in Afghanistan. The event may stop negotiations on a post-2014 presence in the country, and may shift to the issue of legal immunity, which tripped up the post-2011 presence in Iraq. That was in large part animated by the Nissour Square massacre, where Iraqi civilians were murdered by private security contractors. But there’s plenty of reason to pull up stakes, far removed from the situation over the weekend.

And increasingly, Republicans know this. When Rep. Duncan Hunter, the son of the former Armed Services Committee Chair and himself an Afghan war vet, starts calling the situation “untenable,” you know that thinking has shifted.

HUNTER: I think we’re getting into an untenable situation. I think we’re at the point — I don’t want to — ya know you look back at these things through history, through a matter of years and they’ll look different than they look right now with us being here.

But I will say this, if there is a time to possibly think about accelerating turning this into a counterterrorism mission, i’m not talking about leaving Afghanistan, but really reducing the number so that what we’re doing is killing the bad guys, this might be a time to look at that because…what you can’t do is be scared that the Afghan counterpart that you’re training, the Afghan major, is going to shoot you in the back the next time you turn around. That makes a counterinsurgency mission, with the number one goal of training the Afghans, our Afghan counterparts, the Afghan Army, if we can’t trust them to not shoot us in the back, that makes it pretty hard to train them.

I could see a break with the war by the GOP, with Obama left virtually alone on prosecuting it to its conclusion. That may not happen because of the residual pro-war folks on the right, but again, if Duncan Hunter is going there, that’s a sign of a new fault line in US politics.

UPDATE: At least some officials in the White House are working on a faster pullout.