Five years ago this month, American troops liberated Iraq from Saddam Hussein. Then came the hard part.

American intelligence had been wrong about Saddam’s stockpiles of weapons of mass destruction: They were nowhere to be found. Most academic experts had failed to perceive the currents of religious extremism and sectarianism running just beneath Iraq’s secular surface. State Department consultants and U.N. advisors proved unequal to the task of building democratic political institutions quickly from scratch

The media had understated Saddam’s barbarism: It had been too risky to report in depth on the mass graves Saddam filled with dissidents; the tens of thousands of Kurds gassed to death in their villages; the camps where Saddam trained terrorists for assignments abroad. As a consequence, few anticipated how severely Iraqis had been traumatized.

And America’s military, so adept at bringing down a dictator, was unprepared for the “small war” that would follow: terrorist attacks on innocent Iraqis that the “international community” would blame not on the perpetrators -- but on America.

Like most military strategists of the late 20th century, Secretary of Defense Donald Rumsfeld envisioned wars of the 21st century as akin to computer games. Advanced technology, more than blood and sweat, was supposed to be decisive. And in a place like Iraq, it was believed, the U.S. “footprint” should be as light as possible because close proximity to American soldiers would surely incite the natives to violence.

The result of so many errors and misjudgments was catastrophic. Three years after the liberation of Iraq from Saddam, much of the country had been taken over by al-Qaeda. Other areas were under the sway of Iranian proxies, in chaos, or close to civil war.

Iraq’s military had been disbanded by the American envoy, L. Paul Bremer. America’s forces were cooped up in heavily guarded Forward Operating Bases (FOBs) waiting for actionable intelligence that seldom arrived. When it did, they would drive their vehicles to battle down roads their enemies had lined with bombs.

Finally, after the 2006 election rebuke to President Bush, a new Defense Secretary, Robert Gates, was assigned to the Pentagon, and a new commander, Gen. David Petraeus, was deployed to the field of battle. American forces set out to liberate Iraq -- for a second time.

The Petraeus strategy was nothing if not counter-intuitive: He gave the enemy more targets and assigned them to more vulnerable positions – outside the well-guarded FOBs and in the shadowy streets. But once the Iraqis understood why the Americans were there – to defend them from terrorists – they provided a wealth of intelligence. Before long, Americans and Iraqis were fighting side by side against their common Islamist enemies. Continued...