In a ceremony held Thursday in Baghdad, the U.S. military officially ended its mission in Iraq. The approximately 4,000 combat troops still in Iraq are expected to leave the country by Dec. 31.

With that ends a confused and confusing part of U.S. history, one that most Americans are probably glad to put behind them. U.S. involvement in Iraq was by turns divisive, infuriating, embarrassing, tragic and a source of great pride. Sorting that out will take time.

What did this country proud is the only part easy to explain. With rare exceptions, the troops performed magnificently. There were as many as 170,000 U.S. military personnel in Iraq at the peak of the war, and with that, reports of outstanding courage, dedication and selfless devotion to duty became almost commonplace. Tasked with a poorly defined mission in an inhospitable land, the overwhelming majority of U.S. troops lived up to the finest traditions their services and of the United States.

As might be expected, on those few occasions when they did not – the abuse of prisoners at the Abu Ghraib prison, for example – the fault clearly lay with a failure of leadership. As deplorable as that abuse was, though, some cases of such command breakdowns are almost inevitable in an operation as large as the war in Iraq.

They are also made more likely by confusion at the top. A poor understanding of the fundamental mission can only exacerbate the inevitable element of chaos in a combat zone. And the fact is that after almost nine years of war, Americans are still left scratching their heads as to what this was all about.

The stated reason for the initial invasion of Iraq was that Saddam Hussein had, or was about to have, weapons of mass destruction. Although widely disputed at the time, that was at least consistent with the fact that he had sought advanced weaponry and demonstrated a propensity for extreme violence and cruelty. The idea that he might aid al-Qaida further fed that fear.

But a track record of evil behavior is not the same as a credible threat, and no weapons of mass destruction were found.

What was found was a cobbled-up nation riven by ethnic and sectarian conflict and brutalized by decades of tyranny. And with that, the United States took on a different mission. U.S. forces, military and civilian, found themselves trying to build a functioning nation-state out of the rubble of Saddam’s vainglorious dreams, and doing so while in the middle of a civil war.

Have they succeeded? Most Americans would probably say close enough. The country is clearly more stable than a few years ago, and ultimately it is the Iraqis’ responsibility, and the cost of perfection could be infinite. In any case, the American public never signed on to remaking Iraq in our image, let alone permanently occupying it.

Was this war worth it? It is hard to see how.

Almost 4,500 Americans died in the Iraq war, thousands more were wounded, and countless others will bear mental and emotional scars. It must be remembered, though, that those Americans were hurt or killed serving their country and trying to help a long-suffering people. There is great honor in that, and their sacrifice should never be confused with questions about the wisdom of going to war in the first place.

Why the United States invaded Iraq will be debated for some time. After almost nine years, however, it is impossible to see that decision as anything other than wrong.

This holiday season, let us just rejoice that this war is over.