The conventional wisdom on the left for going on five years has been that Iraq was a mistake, that it diverted resources from the "real fight" in Afghanistan. But as Victor Hanson points out, that cuts both ways, and our difficult victory was Al Qaeda's crushing defeat.

2) We were far more able to inflict casualties (given the terrain, geopolitics, and nature of the fighting) in Iraq than in Afghanistan, and that resulted in both more damage to terrorism in general, and a greater sense of deterrence than was true of the fighting alone in Afghanistan/Pakistan. When bin Laden and Zawahiri announced that Iraq was the major front in the terrorist war on the U.S., they raised the stakes, and were in essence inviting terrorists to go there rather than to Waziristan. Note we hear no more from either one of them about winning in Iraq, the central front in Iraq, the need to join jihad in Iraq, etc. Now, it is all Afghanistan again.

This all begs the question: what would the war in Afghanistan have looked like from 2003-2009, had we not invaded Iraq? As our victory in Iraq solidifies and AQ abandons that front, the answer is becoming clear: it would have looked like Afghanistan does now, a difficult, deadly insurgency over terrain that lessens the impact of our advantages in weapons and wealth, in a country that is too poor to sustain the strong central government necessary for any exit strategy that can reasonably be called success, where our drug policies create a huge incentive for desperately poor farmers to join the other side. We might have abandoned the country in defeat years ago, as Obama appears increasingly willing to consider.

Our Mesopotamian "misadventure" bought us several years' worth of relative peace in Afghanistan while dealing a grievous blow to Al Qaeda, by dragging them into a setting where the war was winnable. Like the intervention that allowed South Koreans to remain free, Iraq may never be a popular war, but increasingly it appears in hindsight to have been a strategic masterstroke.