On August 26, 2008, Michael Mullen, the chairman of the Joint Chiefs of Staff, touched down for a secret meeting on an aircraft carrier stationed in the Indian Ocean. The topic: Al Qaeda and the Taliban. The summit had been arranged the previous month. Mullen had grown anxious about the rising danger from Pakistan’s tribal areas, which Islamic militants were using as a base from which to strike American troops in Afghanistan and to plot terrorist attacks against the United States. He flew to Islamabad to see the country’s army chief of staff, Ashfaq Parvez Kayani.