What possible motive does Islamabad have for supporting Afghanistan’s bloody insurgency?

John R. Schmidt in Foreign Policy:

Pakistan_12Secretary of State Hillary Clinton is headed to Islamabad this week for what U.S. officials are billing as a last-ditch effort to patch up ties with Pakistan and urge the country's ruling generals to crack down on the Haqqani network, an Afghan insurgent group based in Pakistan's tribal areas that Washington is increasingly putting on par with al Qaeda and the Taliban as a threat to the United States.

The recent drumbeat of stories about the Haqqanis began when Adm. Mike Mullen, then the chairman of the Joint Chiefs of Staff, called the Haqqanis “a veritable arm of Pakistan's Inter-Services Intelligence agency.” Although less frequently mentioned, the Pakistanis are also providing sanctuary to the other main Afghan Taliban group, Taliban leader Mullah Omar's Quetta Shura, based in Baluchistan province to the south. But very little has been written about why the Pakistanis support these groups. What possible motive, after all, could they have for supporting forces that are engaged in a nasty guerrilla war against their ostensible American allies in Afghanistan? The reason is simple: The Pakistanis fear that if these Taliban forces are defeated, the United States will abandon the country, leaving behind what they believe will be a hostile Afghan government allied to their mortal enemy, India. And if Clinton fails to understand this dynamic, the latest bid to salvage what's left of U.S.-Pakistani ties will end in failure.

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