On November 9, 2012, the mystique that had shrouded David Petraeus for nearly a decade suddenly shattered. That afternoon, he resigned as director of the CIA, admitting to an extramarital affair—a firing offense in the military officers’ code and, though Petraeus had retired from the Army, he still felt bound by the code: at least after he’d been caught.

The news stunned his longtime associates. He’d seemed a figure of such rectitude, had spoken with contempt of other officers who’d committed infidelities. Yet in at least one sense, the lapse flowed naturally from the course of his career.

His mistress, it turned out, was Paula Broadwell, the author of All In: The Education of General David Petraeus, a fawning biography published earlier in the year. More to the point, she was an aspiring denizen of the cabal that he’d created. They’d met in 2006, when she was in graduate school at Harvard and he came to give a talk about COIN. She approached him afterward, expressed interest in the subject. Soon she began a PhD dissertation on his leadership style and, when he took command in Afghanistan, asked if she could come observe him in action. He agreed.

She was twenty years his junior, and beautiful, but her initial appeal lay more in her CV than in her glamour. She’d been a West Point cadet, she’d trained as a parachutist, she was an obsessive runner, and she was an Ivy League grad student. In short, she seemed just the sort of officer-intellectual that Petraeus had long been keen to mentor—a promising candidate for the West Point mafia, the Lincoln Brigade.

But, unlike other protégés, Broadwell didn’t merely admire Petraeus, she adored him—and Petraeus let her, to a degree that discomfited some of his aides. In Kabul, he gave her extraordinarily close access; they ran five-mile jogs at dawn together, traveled together, shared endless hours for weeks at a time. Petraeus had invented his own rules before, though strictly for military reasons. Now, after so many years of deployments, on a turf more primal, the allure proved overwhelming, the famous discipline broke down.

In the end, the decade of war punctured many myths that were long overdue for rethinking. It revealed COIN as a tool, not a cure-all—and David Petraeus as a man, not an icon.