The decisive turn came in summer 2006, when the insurgency exploded across southern and eastern Afghanistan, with depth and skill. It hasn’t been the same since.

Image Gen. Stanley McChrystal Credit... Tyler Hicks/The New York Times

By any measure, 2009 was the most difficult and demoralizing year.

“The Afghan insurgency can sustain itself indefinitely,” Maj. Gen. Michael Flynn, the head of military intelligence, said in a briefing paper at year’s end. Twice as many American troops died in combat in 2009 as the year before. Worst of all: the model of democratic rule painstakingly constructed since 2001 collapsed, in the presidential election, under an avalanche of fraud.

Which brings us to now. The capture of Mr. Baradar, followed by the arrest of two Taliban “shadow governors” in another Pakistani city, suggested that the haven the insurgency’s leaders have used for so long might not be so safe after all. If that proves true, the potential impact — on Taliban operations, on the prospects for a negotiated peace — seemed enormous.

Still, it was the mission in Marja that seemed to bear the most potential, if only because in the end the war’s outcome is going to be decided on Afghan ground. In Marja, the Americans, British and Afghans were implementing the ambitious new strategy championed by Gen. Stanley McChrystal, the top military commander.

Under that plan, killing the insurgents in Marja figured as the least important part of the battle. (As it was, the heaviest fighting appeared to be over by week’s end.) What comes after the shooting, by General McChrystal’s account, is what matters most: building an Afghan government, police force and army that can keep the Taliban out after the fighting is over. Failing to do so — to build institutions to allow the Afghan state to stand on its own — has been the main shortcoming of America’s strategy since 2001.

There are many reasons to believe that General McChrystal’s plan could work. Among his own forces, he has sharply curtailed the use of heavy firepower in order to spare Afghan civilians. He has stepped up the training and recruitment of the Afghan Army and police, to prepare for the day when the Americans and Europeans have left. In Marja, he has insisted that Afghans play a large role, putting more than five Afghan battalions in the field.