With Sir John Chilcot's long-awaited Iraq Inquiry published at last, perhaps lessons from an earlier conflict could prove useful in dealing with many of today’s problems in the Middle East.
In the 2003 film The Fog of War, former US Defense Secretary Robert McNamara reflects on his involvement in the Vietnam War, as well as in World War Two as an army officer.
It was released six years before McNamara's death at the age of 93.
His goal, he says, was always to "develop the lessons and to pass them on". Some of his key insights were:
Empathise with your enemy
McNamara stresses the importance of getting inside the skin of an adversary, so that their actions and their perception of you make more sense.
He admits that in Vietnam, US planners did not understand the North Vietnamese well enough to be able to do this effectively. He says:
"We saw Vietnam as an element of the Cold War, and not what they saw it as – a civil war. We were wrong."
And as a consequence, America lost.
Today, knowing the specifics of Daesh's nihilistic worldview is essential to predicting their next move.
Just as important is using Chilcot’s findings to better understand failures to plan more thoroughly for the sectarian breakup of Iraq. Lessons must be learnt quickly as the turbulence continues.
During his time with the US Army Air Force, McNamara analysed the efficiency of bombing operations launched against Japan from China.
He found that logistical problems made the whole operation highly wasteful and his department recommended changes that would see his commander, Major General Curtis LeMay, devastate Japan from a new launchpad in the Mariana Islands.
This lesson has huge relevance in our own time, though arguably political rather than logistical miscalculations are the biggest problem.
Did a lack of preparation in Iraq make the sectarian violence that helped to spawn Daesh inevitable? Or would global warming and drought have produced the chaos next door in Syria anyway?
Was the decision to support the uprising in Libya the wrong choice, or was it only made so by comparative underfunding of the reconstruction? These are complex questions, but the best answers must be sought if military operations in the Middle East are to be improved.
Proportionality should be a guideline in war
McNamara cautions that effective military operations are no good without moral guidelines to keep their destructiveness in check.
He admits that LeMay’s improvements in bombing operations crippled Japan, but feels guilty about the sheer scale of these missions, saying the total or near destruction of 67 Japanese cities by firebombs, and then two cities by nuclear bombs, was completely out of scale with the military objectives the US was trying to achieve.
US B-29 Superfortress bombers dropping incendiary bombs on Yokohama in 1945
While conflict in the present day is far less devastating than during World War Two, the principle is more relevant now than ever.
"Collateral damage" can mean large numbers of civilian casualties - as many Afghan civilians were killed during the NATO invasion of 2001 as American civilians died during the September 11th attacks.
With porous borders and homegrown terrorism, military campaigns risk becoming victims of their own success if they inspire deadly retribution.
'Belief' and 'seeing' are often both wrong
McNamara admits that the attack on US warship USS Turner Joy that precipitated the escalation of the country's involvement in Vietnam was, in fact, a complete mirage.
McNamara says the attack on USS Turner Joy was a 'mirage'
It was merely confusion, he says, in response to heightened tensions following an earlier naval confrontation between the US and North Vietnam two days before.
The parallel to phantom 'weapons of mass destruction' is obvious.
Be prepared to re-examine your reasoning
The Vietnam War was fought almost solely by the US against the North Vietnamese.
McNamara states that US military power should never be used unilaterally, and that if allies with similar values and interests cannot be convinced of the merits of a military operation, then America should be prepared to rethink.
US tanks in Vietnam
Barack Obama showed restraint in the face of huge public pressure on his allies to not escalate matters in Syria.
Had similar pressure come from British and other foreign leaders in the run up to the Iraq war, perhaps the Bush Administration (or, failing that, the US congress) might not have pressed forward with their plan to topple Saddam Hussein - and today’s Middle East might be less turbulent.
If you'd like to watch the 'Fog of War' you can rent it via YouTube here.