The first is an absence of trust between Washington and Kabul. The longer the Americans stayed the more difficult it became to persuade Afghans that their presence was helpful and their purposes benign. Over time, Hamid Karzai, the West’s chosen leader of “liberated” Afghanistan, came to see the United States as an occupying power — part of the problem, rather than part of the solution. Karzai believed, not without reason, that United States officials paid lip service to his concerns, were willing to cut deals behind his back and on occasion plotted to replace him with someone more accommodating.

For their part, Americans who dealt regularly with Karzai concluded that he was indecisive, unstable and given to bouts of paranoia. When he first became leader of Afghanistan in December 2001, Washington had celebrated Karzai as an Afghan Mandela. By the time he vacated the premises 13 years later, he had become in American eyes an Afghan Mugabe.

Of even greater significance, in Coll’s view, is Washington’s dysfunctional relationship with the government of Pakistan, or more specifically with the Pakistani Army, which effectively calls the shots on all matters related to internal and external security. Pacifying Afghanistan was always going to pose a challenge. Absent full-throated Pakistani collaboration, it would become next to impossible. The United States needed two things from Pakistan: first, that it would permit supplies bound for coalition forces in landlocked Afghanistan to transit its territory; and second, that it would prevent Qaeda and Taliban remnants from using Pakistan as a sanctuary and operating base.

From Washington’s perspective, these expectations, premised on an assumption that Pakistan could be cajoled into complying with America’s purposes in Afghanistan, seemed eminently reasonable. Yet that assumption proved wildly off the mark. While the generals commanding the Pakistani Army and directing the Inter-Services Intelligence made a show of cooperating, they were simultaneously working to undermine coalition military efforts. Imbued with the conviction that Afghanistan is vital to Pakistani national security, they had no intention of allowing the United States to determine its fate. So while accepting subsidies amounting to hundreds of millions of dollars — Washington even elevated Pakistan to the status of “major non-NATO ally” — the Pakistanis still actively supported the Taliban.

Pakistan’s military leaders were playing a double game. United States officials knew they were being had, yet could do little about it. With its own well-established record of having broken promises to Pakistan, Washington was not exactly in a position to call in any markers.

Despite being nominally the superior power, the United States found that it could exert minimal leverage. Officials could ask, but not demand, while Pakistan’s nuclear arsenal limited its susceptibility to threats and sanctions. Although American officials went to almost comic lengths in attempting to befriend or flatter their Pakistani counterparts — Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, called on Pakistan’s army chief no fewer than 27 occasions — such efforts proved to no avail.