When President George W. Bush stood on the deck of USS Abraham Lincoln on 1 May 2003, the mood was euphoric. 'Major combat operations in Iraq have ended', he announced; 'in the battle of Iraq, the United States and our allies have prevailed.'
Despite the infamous banner draped across the aircraft carrier's tower reading 'Mission Accomplished', President Bush was careful to underline the fact that there was still much to be done. 'We have difficult work to do in Iraq', he said, including 'bringing order to parts of the country that remained dangerous.'
Few would have imagined that eleven years later, Iraq would be in a state of meltdown. The surging success of ISIS - a radical Islamic group that has brought swathes of territory under its control - has brought the government in Baghdad to its knees. For some observers, though, it is a case of history repeating itself.
Nine centuries ago, the west staged a dramatic military intervention in the Middle East that was strikingly similar to the massive deployment that removed Saddam Hussein from power. In 1095, Pope Urban II announced to the knighthood of Europe that they had to rise up and fight for their faith against a threat from the Muslim world. If they did not do so, he warned, the consequences for Christianity would be bleak indeed.
With reports that acts of extreme violence were being carried out against the innocent population from the shores of the Bosphorus to the Holy City of Jerusalem, some believed that the apocalypse was at hand. Just as after 9/11 many shared the unmistakable sense that a new era of uncertainty was dawning - where things were no longer familiar and comfortable, but unsettled and dangerous.
In the days after 9/11, some - including the President - spoke in terms of a new Crusade: 'This crusade, this war on terrorism is going to take a while', Bush said on the South Lawn of the White House. 'And the American people must be patient.'
The Pope did not call the struggle with Islamic world 'Operation Enduring Freedom' or refer to the enemy as part of an 'axis of evil', but he might as well have done. The First Crusade was a mission that put western beliefs and values firmly on the line. Just as with Afghanistan and Iraq, this was a struggle of light over darkness.
The knights who set off from home had to rely on extraordinary courage and discipline as they fought off one threat after another. As with the soldiers deployed into Iraq in 2003 and the decade that followed, the experiences were intense and often unbearable - such were the dangers and suffering in order to achieve an almost impossibly ambitious goal thousands of miles from home.
The problem, though, was that all the energy and resources had been directed at taking the Holy City. Little thought had gone into what would happen next. The knights who reached Jerusalem found themselves having to think on their feet about how the city should function, about who should be in charge, about who and what would be needed in the future. Many simply wanted to return home on the basis that the mission had been, well, accomplished.
It was a similar story in Iraq. Attention was spent on the logistics of regime change rather than the aftermath. In the months before the invasion by coalition forces, US Central Command developed a delusional and naïve series of presumptions about how post-Saddam Iraq would look, set out in a series of vapid, superficial and irresponsible PowerPoint slides that epitomise the naivety of the west's engagement in Iraq. Like with the Crusade, there was no exit plan to speak of, no long-term strategy beyond hope and faith.
In the Middle Ages, the real response from the Islamic world took time to form. Muslims had long been divided by petty personal and regional rivalries and by religious squabbling. However, the arrival of the Crusaders sparked a period of consolidation where competition was replaced by the moulding of a single bloc with an overriding raison d'être: the elimination of the foreign occupiers whose presence, beliefs and behaviour were presented as anathema to Islam.
The catalyst was the emergence of charismatic figure who could articulate a coherent vision of unity and deliver results on the battlefield: Saladin. He took on the Crusaders at their own game with an intoxicating blend of faith, military values and personal bravery. He united Muslims from far and wide, if not healing divisions then at least papering them over by focusing on the higher goal of retaking Jerusalem from the Christians and driving the westerners out of the Holy Land.
And that is what is happening with ISIS under the leadership of the murky figure of Abu Bakr al-Baghdadi, about whom little is known other than the time he (and several of his commanders) spent in prison in Abu Ghraib and then Camp Bucca. Successes in Syria last year have been astutely translated into creating a domino effect that Saladin would have recognised and admired: gains of towns like Raqqa have been translated into attracting more support and manpower, enabling momentum to be built up and increasingly large targets to be fixed onto - including Kobane, but also Mosul and Tikrit, birthplace of both Saddam Hussein and Saladin.
Like Saladin, who controlled his image carefully, ISIS have proved shrewd operators in the propaganda war, focusing on their primary constituency: young motivated jihadists, keen to give humiliate outside interlopers and beat them at their own game.
The images of torture, extreme violence and executions that have mushroomed over the last few weeks are designed to shock - but they are also intended to position ISIS as doers rather than talkers. And that, as Saladin's followers found out, is extremely attractive to those who can only see inertia, inefficiency and corruption in the system created after Saddam's fall.
The West brought about the rise of Saladin and ISIS. And as the Crusaders found, you reap what you sow. For it turns out that the hard part is not the conquest, but what happens after that really matters - as history teaches us. If only our politicians and strategists wanted to learn: for one thing, they'd have been expecting the violence of the reaction - and would not be caught cold, making it up as they go along.