The four letter word that has dominated America's political discourse over the last decade has resurfaced in the US presidential race. At the weekend Rick Perry, one of the Republican candidates, claimed his presidency would return US troops to Iraq. "The idea that we allow the Iranians to come back into Iraq and take over that country, with all of the treasures, both in blood and money, we have spent ... is a huge error for us," he said.
Iraq has now factored into three US presidential elections. US troops left Iraq last month after spending the better part of a decade between the two rivers, but can America ever move on?
Over the last three weeks, I've written about the legacy of the Iraq invasion and why it is, and will continue to be, so hard for Iraqis as a people and a nation to close one chapter and open the next.
The repercussions of the shattering of that country will be felt for years and decades. Breaking a country so brutally means it cannot easily be put back together.
The knock-on effects are subtle and long-lasting: the huge mental health problems, the trauma of losing family members, the effects of having educations and careers interrupted. Combine that with the flight of those with the intellectual or financial resources to leave, the scrabbling for political power and resources, the limited implementation of the rule of law, and it is clear the collective capacity of the country to rebuild itself has been severely depleted.
The American invasion will continue to define Iraq for a generation. But it will also define America, at home and abroad.
For those directly affected by Iraq, the wounds of the war may never heal. All across America from the traditionally conservative families that staff America's military, there are thousands of families who have lost loved ones or whose children came back from Iraq broken physically or mentally. That harm may never fully heal.
It has become fashionable to speak of Iraq as this American generation's Vietnam. In some respects, this is fanciful: both wars grew out of particular political circumstances, four decades apart, which bear little relation to each other. The schism in US public life over Vietnam was also far deeper.
Yet in other respects, there are parallels. Both were hugely divisive wars that went to the core of American life, exposing and hardening divisions within society. In the run-up to the Iraq war, pundits confidently predicted the conflict would banish the ghosts of Vietnam. Instead, new ones have been created.
The Iraq war has had serious repercussions for America's standing in the world. Historians will debate for decades whether the Iraq war can be boiled down to a win or a loss, but the long conflict showed clearly the limits of America's power.
It also showed the limits of its will - after so many years and so much blood and treasure, in the end the Americans left Iraq in a far worse state than they found it, essentially surrendering the battlefield to their most intractable enemy Iran. That is a very different message for America's enemies than during the Vietnam era, but no less salient. The Taliban in Afghanistan have learnt that lesson and will doubtless aim to capitalise on it, as will the belligerents of America's future wars.
This is why Americans can't let go, why the ghosts of Iraq will long haunt US public life. Iraq was troublesome from the beginning: the weapons of mass destruction that didn't exist; the apparent involvement of Al Qaeda that only became real after the invasion; the concocted connections between Iraq and the perpetrators of the attacks of September 11, 2001. All of those were present at the beginning, before the grey fog of war, before Abu Ghraib, before Falluja.
If, in the end, the war could be called a clear win, the bitterness of those memories could be blunted. But with Iraq rapidly getting worse, with Iran gaining strategically as a direct consequence, these schisms cannot be swept from politics. Blame must be apportioned.
In a very real sense, the battle over the war is far from over: President Barack Obama came into office opposing it, only to preside over a surge in troops on the ground, and ended up withdrawing America's military by following a plan brokered by George W Bush. There are no clear-cut answers, no talking points memos.
The American invasion of 2003, and the war of 1991, were not static events. They were not dips in the timeline of history. Rather, they shaped all the events that came after, changing the course of Iraqi history irrevocably.
The neoconservatives around Mr Bush frequently painted the 2003 invasion in two separate ways: either as a short, sharp shock that would put Iraq back on to a prosperous path, or an historic moment that would reshape the entire Middle East. The latter didn't happen, but neither did the former. In truth, the invasion of Iraq changed the history irrevocably.
And the history of America. As with Vietnam, which was also meant to be a short, sharp war, it will colour every military calculation for decades. The tactics, the politics, even the equipment of America's future wars will be shaped by the Iraq experience.
War is a catastrophic event and like all catastrophes, it ties participants together, willingly or not. In this last decade in Iraq, both America and Iraq were aggressors and victims, as individuals from both countries were aggressors and victims. The tragedy for both countries is that this chosen war could so easily have been avoided, that there was no inevitability to their tragic embrace, an embrace from which neither can now easily extricate itself.
Follow on Twitter: @FaisalAlYafai