The Spanish philosopher Santayana said: "Those who do not remember the past are condemned to repeat it."
It's that trap the three officers who wrote the British army's 2006 analysis of military operations in the north were trying to ensure the army would avoid in any future campaign.
Of course their take on the history of the past 40 years is self-serving and self-congratulatory. What else would you expect? Of course it's full of elementary errors, wrong dates and so on.
They're not so hot on contemporary British history either, when they talk about Blair's attempt in 2005 to extend the 28-day detention period to 60 days when it was in fact 90 days.
However, as it says in the foreword, "It is not intended as a history" of the Troubles.
They probably didn't care too much if they got certain details and events wrong.
What they were concerned about was strategy and tactics at the highest level and here the report is very instructive and candid.
One central point is repeated again and again, perhaps half a dozen times in different words. It's this: there was no-one in overall charge here.
The authors point out that the GOC here was not responsible to the secretary of state but to the chief of the general staff (CGS) who issued directives to the GOC.
Indeed the report itself is for the CGS who contributed a foreword. CGS was responsible to the secretary of state for defence.
As the report says, the "net result was incoherence".
There was a "lack of a single military authority for the campaign" here.
There was "no thread of purpose" in the campaign.
This absence led to "purposeless activity".
For example, troops often patrolled for the sake of patrolling.
There was a "lack of coherence" between the secretary of state and NIO and the security forces.
At the very top, in the Northern Ireland joint security committee where politicians and the various security forces met, for years there was no agenda circulated and no minutes kept.
Each branch just went about its own business.
In 1972-4 the secretary of state was releasing internees while the army was busily arresting men for internment: 60% of internees released in 1972-3 rejoined the IRA immediately. It was a merry-go-round.
A strong sense of frustration with politicians runs through the report. Apart from incoherence and no political direction, the complaint is that no British politician could see the big picture: social and economic or political.
In one telling example they say that instead of sending three battalions into Divis in the seventies the NIO should have sent in a bulldozer and replaced the flats with decent, respectable homes for people. That didn't happen until 1986.
Another candid admission and warning for future exercises is that the army can make any situation worse.
The report's authors accept the British army did exacerbate matters here by alienating the Catholic community in 1970 and 1971 in acting at the behest of the unionist regime in Stormont. Repeated house searches, heavy-handedness, then internment itself produced an insurgency which lasted until the mid-seventies.
Only then did IRA activity take on the shape of a long-term terrorist campaign.
The question asked is why, when so much had been learned and all the procedures were in place by 1980, did it take another 18 years for the Good Friday Agreement to emerge?
The answer, which the report does not provide, is that the Thatcher government wasted the eighties in the futile search for a military victory. It was not until she was gone that the new Conservative leadership in 1991 felt able to explore the contacts republicans had tried to open up after the 1985 Anglo-Irish agreement.
Have any lessons been learned?
In the foreword, the then CGS Sir Mike Jackson says the lessons have already been put into practice in the Balkans, Iraq and elsewhere. Hard to believe when you see British troops beating and torturing Iraqis, kicking in doors and wrecking peoples' homes in what are euphemistically called house searches.
In Kosovo in 1999 those famous community relations workers, One Para, shot and killed three Albanians celebrating the arrival of NATO. Just like old times.