Until recently, the ground-level conduct of the Taliban’s war against the U.S.-led coalition has been left to local commanders acting on their own. Mr. Omar, who heads a Taliban leadership council called the Quetta “shura” — named after the city in southeast Pakistan where it is believed to be based — has typically focused on choosing Taliban leaders and funneling money, religious guidance and strategic advice to fighters.

But since the start of the year, through his direct lieutenants, Mr. Omar has ordered a spate of suicide bombings and assassinations in southern and eastern Afghanistan that presage a bloody phase to come in the Afghan war, according to U.S. officials and Afghan insurgents…

“This is Quetta’s answer to Obama’s surge,” said a senior member of a militant network led by Gulbuddin Hekmatyar, an independent Afghan warlord who fights alongside the Taliban. He was referring to plans by the administration of President Barack Obama to send an additional 21,000 troops to Afghanistan over the next few months. The Quetta “are not ready to lay down their weapons,” he said in an interview in the Pakistani city of Peshawar…

Mr. Omar’s push to centralize command has irked some rank-and-file Taliban, insurgents say, potentially leaving them more amenable to U.S. and Afghan outreach efforts. Drawing on a tactic first used in Iraq, the U.S. has been reaching out to moderate Taliban fighters in the hopes of reconciling them into Afghanistan’s political process.