Petraeus moved up to take over our Central Command, or CENTCOM, where he faces the gritty challenges of the world's strategic junkyard, the greater Middle East: No rest for the victor. But we can pause to consider what he achieved:

Two years ago, many Americans believed Iraq was hopeless. Personally, I'd begun to despair of the administration ever fighting to win. Without a sharp change in policy and practice, our effort to bring democracy to a wretched population would end by discrediting democracy and unjustly humiliating our military.

In "politics above country" Washington, partisan Democrats celebrated our impending defeat, salivating over American casualties as vote-getters. Repeatedly, they sought to deny our troops the resources they needed to fight and survive.

Then, in a very dark hour, two things happened. Realizing - at last - that former Defense Secretary Donald Rumsfeld had failed him, our president backed a hail-Mary-pass troop surge to give Iraq one last chance. And he chose a new commander, Petraeus.

We all know what happened: Iraq turned around with a speed that bewildered the experts.

In the 19 months of the Petraeus era, Iraq evolved from a bloody landscape sliding toward civil war to a land of hope. Urban combat and a literal reign of terror have been replaced by the spreading rule of law, a blossoming economy, LA-quality traffic jams - and the political squabbling that accompanies democracy.

As Petraeus is always the first to note, much remains to be done and much could still go wrong. But every single trend line has turned positive. Al Qaeda's grip has been broken. (It can still set off bombs, but can no longer set itself up as a champion of Sunni Muslims.) Our troops are coming home at a steady pace. And (dare one say it?) we're winning.

That last point's a sore one. Scrupulously avoiding any statement or action that played politics, Petraeus nonetheless changed the terms of our presidential election.

A year ago, the big issue was Iraq, which Sen. Barack Obama insisted remained a disaster. Now the campaign is a contest of qualifications - and character.

Of course, Petraeus had a lot of help - he's always the first to point out that a successful command is a collective achievement. But the huffy claims that it was this, that or the other thing that "really" brought about positive change in Iraq fail to grasp what Petraeus got from the start: There's never a single solution to an insurgency.

Yes, a handful of savvy US officers had begun to grasp the opportunity to "flip" the Sunni tribes of Anbar to our side even before Petraeus took command. But Petraeus recognized a greater potential and expanded the effort dramatically: He turned a promising local business into a nationwide franchise.

Yes, the surge gave Petraeus more flexibility than his predecessors had. But the critical difference was that he employed our troops differently, sending them into neighborhoods to stay and provide security for the people. And he exploited the surge's psychological effect - convincing allies and enemies alike that we weren't about to quit. Without that reassurance, the turnaround wouldn't have happened.

And yes, we were even lucky in the extremism and cruelty of our enemies - both al Qaeda's butchers and Muqtada al Sadr's gangsters. They quickly wore out whatever welcome they had among the people.

Yes, Petraeus assumed command at a fortunate time, but Napoleon wanted lucky generals for good reasons. And opportunities are worthless if unexploited.

Always competent in his earlier career, Petraeus rose to greatness over the last two years. Dismissed by a few jealous peers as a "Pentagon prince," he turned out to be the "fightin'est" general we had.

On the home front, the defeat-is-virtuous crowd had talked themselves into believing they were getting a Gandhi; instead, we got a Grant. No previous US commander in Iraq remotely approached Petraeus' relentless determination to track down and kill the enemy's senior leaders. (Think that didn't make a difference?)

Petraeus now stands in a long line of great captains who fought in Mesopotamia, a line stretching back past Alexander the Great to the conquering kings who haunt the Old Testament. Yet there's a crucial difference in the case of this American warrior: He didn't come to conquer, but to offer freedom.

Appalled by our military's success, the media played down the change-of-command ceremony. But history will give Petraeus his due. Meanwhile, a few words from a great poet will serve for this magnificent general who now turns to Afghanistan: "Not fare well, but fare forward."