SpyTalk

Concern over the reliability of Pakistan's officer corps has heretofore focused on the ISI, or Inter-Services Intelligence service, which was wedded to CIA-backed fundamentalist Afghan rebels fighting to oust the Soviet Red Army during the 1980s. A faction of ISI officers is said to remain loyal to the fundamentalists.

The defection of regular army officers to fundamentalist rebels advancing through the Swat Valley toward Islamabad would add another wild card to various nightmare scenarios for Pakistan, a nuclear-armed nation.

Arthur Keller, a CIA spy handler in Pakistan in 2006, told me that he had personally encountered treachery in the army.

"I know of at least two instances from my brief time in Pakistan where we found Pak officers sabotaging the CIA's work in favor of the Taliban and/or al Qaeda," Keller said by email Monday.

And there were similar alarming incidents, said an intelligence source who demanded anonymity.

In 2005 American eavesdroppers overheard a Pakistani officer tipping off the Haqqani network -- the most dangerous, al Qaeda-linked Afghan rebel clan -- of an impending raid against it. 

In another instance, ISI's Directorate S, in charge of external operations, such as Kashmiri independence militants, was releasing militant suspects arrested by ISI's counterterrorism Directorate C.

All of which adds to the portrait of a Pakistan on the vortex of a fundamentalist religious revolution, perhaps along the lines of Iran's in 1979.

But others say the turmoil reflects century-old ethnic tensions, a product of Great Britain's arbitrary delineation of Afghan and Pakistan border in the 19th century.

"To American eyes the struggle raging in Pakistan with the Taliban is about religious fanaticism," the eminent southwest Asia scholar Selig Harrison wrote in Monday's Washington Post.

"But in Pakistan it is about an explosive fusion of Islamist zeal and simmering ethnic tensions that have been exacerbated by U.S. pressures for military action against the Taliban and its al-Qaeda allies. Understanding the ethnic dimension of the conflict is the key to a successful strategy for separating the Taliban from al-Qaeda and stabilizing multiethnic Pakistan politically," Harrison wrote.

"The Pakistani army is composed mostly of Punjabis. The Taliban is entirely Pashtun," Harrison noted. "For centuries, Pashtuns living in the mountainous borderlands of Pakistan and Afghanistan have fought to keep out invading Punjabi plainsmen."

Harrison argued that "sending Punjabi soldiers into Pashtun territory to fight jihadists pushes the country ever closer to an ethnically defined civil war, strengthening Pashtun sentiment for an independent "Pashtunistan" that would embrace 41 million people in big chunks of Pakistan and Afghanistan."