Mark Bowden, author of Blackhawk Down:

President Bush made a courageous decision in the summer of 2006 to reverse direction, but not the reversal sought by Congress (including then-Sens. Barack Obama and Joe Biden), the American public, the overwhelming majority of the press (including this newspaper), and even most of his own military advisers. Instead of cutting our losses and pulling out of Iraq, as we did in Vietnam, Bush doubled down. He invested more troops and, more important, embraced an entirely new strategy.

And Bush was right. What had happened beneath all of the politics was a small revolution in war-fighting philosophy, championed and implemented by an unlikely military leader, Gen. David Petraeus, a soldier/intellectual molded as much by the think tank as the battlefield. He calls the movement his “Counterinsurgency Nation,” and it has rewritten the way America fights. It is not a completely new idea – there are few of those in the study of war – but its basic principles came into clearer and clearer focus as a new generation of military officers fought in Afghanistan and Iraq. Its guiding principle is simple: The prize in these countries is not territory, but people.

Now President Obama must decide whether to let this new generation of battle-tested soldiers apply what it has learned to Afghanistan. Those who argue that the methods employed in Iraq will not work in Afghanistan are right and wrong. They are right that the two conflicts are not identical. What worked in Iraq will not apply in all cases in Afghanistan. But they are wrong to assume the lessons of Iraq have no application in Afghanistan. The counterinsurgency consensus grew out of experience in both wars. America’s new military leaders have been managing both conflicts simultaneously for most of this decade, and the hard-won lessons they have learned derive from both.

I am not a military expert, but I suspect that most wars that last for more than a few weeks follow a roughly similar trajectory. Established generals misjudge the war, and once the battle is joined, a generation of younger leaders discovers the truth, adapts by hard necessity, making life-and-death decisions on the battlefield, and learns, often by trial and error, how to define and fight the new war on its own terms. If the national leadership is smart enough to embrace this knowledge and experience, as Bush was, the tide turns.

There are a number of excellent studies that document this turnabout, notably Thomas Ricks’ The Gamble, Linda Robinson’s Tell Me How This Ends, and Kimberly Kagan’s The Surge. The Iraq war is not over, of course. It remains to be seen if Iraqis can forge a nation from its various contending factions, but there is no denying the extraordinary reversal engineered by Bush, Petraeus, and the remarkable soldiers who have risked and all too often sacrificed life and limb for the last six years. They accomplished it amid a persistent chorus of critics and doomsayers – doomed was actually the word then-Sen. Biden used to describe Petraeus’ chances in April 2006.

Counterinsurgency doctrine is as warm and fuzzy as war can get. It embraces distinctly liberal, humanistic values like protecting civilians, cultural sensitivity, and rigid adherence to ethical standards and the law. It is geared toward partnership, not dominance, and always seeks to minimize violence. In Iraq it rapidly (in months) isolated the murderous extremists who were trying to provoke civil war. The new effort set up a sharp contrast between their methods and goals and America’s. As one Marine officer, Col. Julian Dale Alford, said