(1) General David Petraeus with his troops in Helmand Province, Afghanistan.

(2) As a young paratrooper in the late 1970s, Petraeus read Counterinsurgency Warfare by the retired French officer David Galula, who argued that this sort of war required not just killing the enemy but reforming the government and building up the economy.

(3) Colonel George “Abe” Lincoln started a Social Science Department at West Point just after World War II, realizing that the Army needed officers educated in politics and economics, not just war. This style of thinking would warm its adherents to Galula’s ideas. Lincoln also created a network of “Sosh” graduates, nicknamed “the Lincoln Brigade,” which persisted in Army circles for decades.

(4) Petraeus served as General John Galvin’s aide-de-camp in the early ’80s, then as his assistant in Central America a few years later, his first exposure to insurgency wars.

(5) Lieutenant Colonel John Nagl, one of Petraeus’s West Point protégés, wrote a book comparing the British army’s victory in Malaya with America’s defeat in Vietnam, then, as a high-level assistant in the Pentagon, lobbied his superiors to adopt a COIN strategy in Iraq.

(6) David Kilcullen, an Australian officer-scholar on loan to the Pentagon, and later an assistant to Petraeus in Iraq, was pushing for a similar shift. He and Nagl formed a tight friendship and an alliance for the cause—though Kilcullen later grew disillusioned.

(7) Eliot Cohen, a professor and Pentagon consultant, gathered thirty counterinsurgency specialists to discuss a better way to fight in Iraq. This marked the beginning of an insiders’ community that pressed for a change in war policy—and in the Army’s culture.

(8) Kalev Sepp, an ex–West Point professor, wrote an article for Military Review on COIN “best practices,” which widely influenced the inner circle of the strategy’s advocates.

(9) Sepp and Colonel Bill Hix (right), a West Point Sosh “mafia” grad, briefly convinced the US commander in Iraq, General George Casey (left), to adopt COIN, but later Casey changed his mind and pushed for a speedy troop withdrawal.

(10) Casey’s deputy, General Pete Chiarelli, a former Sosh professor, pushed for COIN but was overridden by Casey. Celeste Ward, Chiarelli’s political adviser, wrote a paper concluding that the war was hopeless as long as the US and Iraqi governments’ interests diverged.

(11) Petraeus, back from a triumphant campaign in Mosul, Iraq, held a conference to vet a new Army field manual on COIN. His cosponsor, Sarah Sewall, director of Harvard University’s Center for Human Rights Policy, helped legitimize the COIN concept among Iraq war critics.

(12) Conrad Crane (right), a classmate of Petraeus’s at West Point, led the COIN conference and helped write the manual, along with Nagl, Kilcullen, Sepp, Cohen, and others.

(13) Shortly before Petraeus returned to Iraq, Frederick Kagan, a former West Point history professor now at the neocon American Enterprise Institute, wrote a paper arguing for a troop “surge” and a shift to a COIN strategy in Iraq.

(14) Kagan received behind-the-scenes assistance from his former office mate at West Point, Colonel H. R. McMaster, who’d led a successful COIN campaign in Tal Afar, Iraq. McMaster’s promotion to general, after being twice blocked by traditional officers, was seen as a sign of change within the Army.

(15) General Jack Keane, a pioneer in the Army’s COIN training centers, circulated Kagan’s “surge” study among senior officials and urged President Bush personally to replace George Casey with Petraeus.

(16) Keane also slipped the briefing to General Ray Odierno, a former door-bashing commander who’d been converted to COIN. Emma Sky (far left), a British Arabist, was a crucial adviser to Odierno, helping him understand Iraqi militants’ motives.

(17) While at Leavenworth, Petraeus cultivated a back channel to Meghan O’Sullivan, Bush’s special assistant on Iraq.

(18) Colonel Sean MacFarland, a former Sosh cadet who’d succeeded McMaster at Tal Afar, crafted a COIN campaign in western Iraq’s Anbar Province, along with the charismatic Sheikh Abdul Sattar, convincing Sunni militants to ally with US forces against jihadists.

(19) General Stanley McChrystal, a Sosh graduate, tried to apply the COIN formula in Afghanistan with the encouragement of Defense Secretary Robert Gates (who switched from skeptic to supporter), but the formula didn’t fit.

(20) Petraeus replaced McChrystal after a press scandal, assuring President Obama that he could make decisive progress within a year, but Afghanistan stumped him too. He ended his tenure exhausted, his COIN strategy discarded, and his career ambition to become Joint Chiefs chairman out of reach. Obama named him CIA director, a job he came to cherish, until a personal scandal—shocking but, in a sense, not so suprising—forced him to resign.