Together, the arrest of Mullah Kabir, Mullah Baradar and the others appeared to mark a shift in Pakistani behavior. Although the motive remains unclear, the change is significant.

“This indicates Baradar was not a one off or an accident but a turning point in Pakistan’s policy toward the Taliban,” said Bruce Riedel, a senior fellow of Brookings Institution and a former C.I.A. official. “We still need to see how far it goes, but for Obama and NATO this is the best possible news. If the safe haven is closing then the Taliban are in trouble.”

For years, Pakistani military and intelligence leaders have supported the Taliban, and allowed their leaders to carry on unmolested inside Pakistan, even as Pakistan’s leaders claimed to be allies of the United States.

The Pakistani interest in the Taliban has always been as a means to influence events inside Afghanistan, particularly if the Americans leave.

Also on Monday, Hajji Zaman Ghamsharik, an Afghan warlord accused of helping Osama bin Laden escape from the Americans at Tora Bora, was assassinated by a suicide bomber wearing an explosive vest. The bomber killed him and 14 others as they gathered at a ceremony to distribute land to returning refugees at a village in his tribal stomping grounds near the eastern Afghan city of Jalalabad.

He had so many enemies that his assassination was not particularly surprising. There was a blood feud between him and the family of another warlord, which blamed Hajji Zaman for his assassination in 2002. There were rivals to his large and powerful Khugiani tribe in Nangarhar Province, and rivals within the tribe. And there were furious American Special Forces and C.I.A. operatives who believed that he was a mercenary who took money to join the fight against Al Qaeda, but then helped arrange Mr. bin Laden’s escape.

Taliban insurgents in Afghanistan are usually quick to take responsibility for suicide bombings. Not in this case; when asked about Hajji Zaman’s killing, the usually garrulous Taliban spokesman, Zabiullah Mujahid, said he did not know who did it.