The Pentagon’s Wars: The Military’s Undeclared War Against America’s Presidents by Mark Perry Basic Books, 341 pp., $30.00

It was August 2004, and the Iraqi insurgency was raging in Anbar province. Major General James “Mad Dog” Mattis of the Marines, who is now the Trump administration’s defense secretary, called a meeting with a group of religious leaders outside Fallujah. His division was coming under daily fire from both local militants and foreign terrorists associated with al-Qaeda’s affiliate in Iraq, and he hoped to persuade the leaders that it was misguided of them to encourage local young men to pick up rifles and shoot at American forces rather than trying to throw out al-Qaeda, whose bombings and beheadings were transforming their province into a hellscape.

“How could you send your worshipers, some of them young boys, against us when their real enemy is al-Qaeda?” Mattis asked them, according to the military analyst Mark Perry in his new book, The Pentagon’s Wars: The Military’s Undeclared War Against America’s Presidents, a history of high-level Pentagon decision-making and of relations between uniformed and civilian executive branch officials over the past quarter-century. Perry goes on to repeat further details about this meeting drawn from Bing West’s The Strongest Tribe: War, Politics, and the Endgame in Iraq (2008). When the religious leaders continued sipping their tea, Mattis shouted: “They’re kids…. Untrained, undisciplined teenagers. They don’t stand a chance.” Later, Mattis told West that the tribes at the time “only saw us as the enemy”; what was needed was for al-Qaeda’s militants to make mistakes and “expose themselves for what they were.”

Al-Qaeda’s tactics did eventually repulse Anbar’s tribes enough for them to band together in the so-called Sunni Awakening and drive the foreign terrorists out. The reprieve was temporary; the remnant of al-Qaeda’s Iraq affiliate would regenerate across the border in Syria, rebrand itself as the Islamic State, and sweep back into Iraq in 2014. But for a few years, Anbar became a somewhat less dysfunctional and dangerous place, as Mattis had thought it could be.

More than a decade later, Mattis, now in a civilian position, is once again trying to navigate a tricky and dangerous situation. Widely regarded as one of the “grown-ups” in the idiosyncratic Trump administration, he is among the striking number of military men with whom Trump has chosen to surround himself. Trump appointed another retired four-star general, John Kelly, as his homeland security secretary, then elevated him to White House chief of staff. He made an active-duty three-star general, H.R. McMaster, his national security adviser. McMaster’s chief of staff is a retired three-star general, Keith Kellogg, and many of the lower-level policy specialists gradually succeeding Obama-era holdovers at the National Security Council also have military backgrounds. As a result, the upper reaches of the executive branch, which felt at times like a law firm…