Graham Leicester: Why it's wrong to scapegoat Blair over Iraq

Tickets are limited and will be allocated by ballot, as if this were a national sporting spectacle. One-third are reserved for families of UK citizens dead or missing in Iraq.

He is scheduled to appear for a full day, giving evidence for six hours. It will be like an extended edition of Michael Buerk's radio programme The Choice. Finally, our former prime minister will be called to account for his actions and we will get to the bottom of his fateful decision to take us to war.

At least, that is the way it is billed. In reality, we cannot expect anything quite so clear-cut. We are not likely to hear anything we have not heard before. He will tell us he did what he felt was right, for the UK and for the international community.

Could he have acted differently? Yes. With hindsight, does he wish he had done so? Not a fair question: we are carried forward on a tide of events and must make our judgment in the moment. Of course he wishes things had turned out differently.

There were different paths that the process might have taken – if the UK and the United States had been successful in gaining a resolution of the United Nations Security Council in March 2003, for example. Or if more attention had been paid in the US defence department to post-war planning. He worked tirelessly at the time, used every tactic he could, called in every favour, to have things turn out differently.

But they didn't. The process led inevitably to a point of decision to join the Americans in the use of military force or not. There come times when prime ministers have to make "tough choices" – and this was one of them. He will stand by it.

Just look back at the debate in the House of Commons on 18 March, 2003, sanctioning military action. The resolution, carried by 412 to 149, sets out in a single paragraph the accumulated hopes and fears of the UK government at the time – the legal grounds for invasion in previous UN resolutions, the exhaustion of the UN process, the need to disarm Saddam Hussein, the parallel moves to stabilise the Middle East and the intention to move rapidly post-war to the reconstruction of Iraq on the basis of human rights and the rule of law.

Blair's opening speech on that occasion is pregnant with the importance of the moment. "This is a tough choice indeed," he said, "but it is also a stark one: to stand British troops down now and turn back, or to hold firm to the course that we have set. I believe passionately that we must hold firm to that course… The outcome of this issue will now determine more than the fate of the Iraqi regime and the future of the Iraqi people… It will determine the pattern of international politics for the next generation."

We can, and will, argue for a very long time about whether the decision was the right one. What is not in dispute is that things did not turn out as planned. The military action was highly effective. The "war" was over remarkably quickly. But the chaos that ensued, the breakdown of order and infrastructure, hamfisted US-led efforts to respond that only encouraged dissent and fuelled the insurgency, have led to a long, drawn-out struggle that continues still.

The final US troops are not expected home until the end of 2011.

We may have "won" the war, but we definitely lost the peace. If this episode has "determined the pattern of international politics for a generation", as Blair suggested it would, then we had better learn the lessons pretty sharpish: we do not want to repeat this pattern again. Which is why, I suggest, the Iraq Inquiry has been established. Its terms of reference are not to name the guilty men. That might satisfy an understandable desire for "justice" and "closure", but does not advance the future cause.

Sir John Chilcot has been asked to examine "the way decisions were made and actions taken, to establish, as accurately as possible, what happened and to identify the lessons that can be learned".

This episode is about far more than an individual, or a critical moment of individual choice. A cursory reading of any part of the evidence already presented to the inquiry shows that.

A succession of witnesses have relived in graphic detail the pressurised realities of modern policy-making. Simple answers and conclusive evidence are horribly elusive. It is a gripping tale of looming and inevitable tragedy, but which holds out the hope of a very different outcome at every turn: "Some days, we felt we were making progress towards the goal, and on other days, we clearly felt we weren't".

Running through the whole inquiry is a search for certainty, evidence, understanding, something unequivocal – the "smoking gun". But, just as we could not find it in Iraq, so we will not find it in this inquiry. As Sir Jeremy Greenstock put it in his evidence, "Like one of those irritating puzzles, once you have got one ball in the slot, when you tipped in the other direction to get another ball in the slot, the first ball slipped out. That was our constant experience".

This will remain forever an episode shot through with ambiguity and might-have-beens. Thinking has changed considerably, particularly in military circles, since the failures in Iraq. The inquiry will have done its job if it signals how to cope better with such issues in the future.

However, like the Truth and Reconciliation Commission in post-apartheid South Africa, its greater value may lie in the honest telling of this story from multiple, personal perspectives, in public gaze and before those most wounded in the process. In this way – perhaps only in this way – and only if we are open to it, after the tragedy will come catharsis.

Graham Leicester is director of the International Futures Forum.