Historians seeking to disentangle the complex motives that led George W. Bush to launch a second war in Iraq will have difficulty in explaining rationally the depth of the antipathy that he and some members of his administration seem to have developed against that country in the first couple of years of his presidency.
That antipathy led them to take the huge risk of invading Iraq against the tide of world opinion and in the absence of clear UN authority, and without any serious consideration of the consequences of their inevitable military success.
It is hard to believe that a war would ever have been initiated had there been a rational calculation of US long-term interests.
Such a calculation would be based on an objective and informed analysis of the likely reactions of many in Muslim Iraq, or of the damage that such a unilateral action would inevitably inflict on the influence of the US worldwide.
A disturbing feature of the affair has been the role played by the intelligence services of the US and Britain.
In the nature of things, such organisations depend for their existence on their political masters. Therefore there must always be some danger that they may succumb to pressure to tell these masters what they want to hear.
But in this instance a further problem may have been that, in dealing with a repressive dictatorship such as that of Saddam, they became over-dependent upon, and perhaps over-credulous about, human intelligence from refugee sources who had an evident interest in securing an American invasion.
Except in rare cases such as Cuba, with its Soviet missile sites 40 years ago, good human intelligence is ultimately more important for decision-makers than other forms of spying.
Deficiencies in western intelligence services had already been demonstrated conclusively 14 years ago when they failed to identify the huge exaggeration by East Germany of its GDP.
This contributed to Chancellor Helmut Kohl's unwise decision to exchange D-marks for ostmarks at par, a decision the consequences of which may still be contributing to slow German growth 14 years later.
Within the disordered US system of government, foreign policy seems in recent years to have been largely determined by the Pentagon rather than the State Department.
The Secretary of State, Colin Powell, seems to have advised against the invasion of Iraq.
Yet, having so advised, he then failed to take the action required in circumstances where, correctly as it turned out, he saw the vital interests of the US being threatened by a fundamentally misplaced political decision.
His failure to resign seems to have been influenced by the sense of loyalty that members of a US administration - and especially a former general - feel towards a head of state, who is also commander-in-chief of the armed forces.
(The contrast between a country with an executive head of state commanding the armed forces and one that is a parliamentary democracy was dramatically displayed last year in relation to this same Iraq war. The head of the British armed forces seems to have told his government five day before that war started that he would not be able to order his troops into action unless he received from the attorney-general an unambiguous statement that in his view such action was authorised by UN Resolution 1441).
We have had our own experience in Northern Ireland of problems created when a ministry of defence is allowed to influence policy or to pursue its own departmental agenda in the course of its implementation.
In the case of Iraq, the justified self-confidence of the Pentagon about its army's capacity to win a war proved hugely damaging to the immediate post-war situation.
For this military self-confidence seems to have prevented any steps being taken to ensure that the army would be prepared and able to handle the aftermath of its victory.
It could have done this in the short-term by being ready to prevent looting, and in the medium-term through being prepared to act as liberators rather than as occupiers.
It may well be, of course, that even if steps had been taken to prepare for the post-war situation, the armed forces of a superpower like the US would still have found it difficult to shift overnight from a combat role to one of peace-keeping - as we in Europe understand that term.
It would appear that, because of its long experience in Northern Ireland, the British army in southern Iraq appears to have been able to make this difficult transition much more successfully.
To be blunt about it, even when faced with the atrocious treatment meted out to four Americans by an Iraqi mob, a serious peace-keeping force in a liberated country would not have been allowed to announce that it was going to "punish" the people of the town they claim to have liberated.
Nor would such a force, if under UN command, ever have been allowed to launch an attack on such a town involving the killing of 600 people.
Even if the violence dies down, and the UN manages to establish a genuinely representative provisional government in Iraq - and this may now happen as the US seems to have given up on its attempt to create a government to its own liking - it is difficult to see how such a government can re-establish calm and prepare for elections if it has to depend for the maintenance of order upon compromised US forces.
There now seems little chance of them being put under UN command or subjected to UN rules of engagement.
At the same time, having made the mistake of standing down the Iraqi army after the end of the war, the process of re-establishing under UN auspices an effective Iraqi force capable of undertaking that task on behalf of the promised provisional government has been left far too late.
That's why it is difficult to be optimistic about the prospects for Iraq during the remainder of this year even if the conflict now under way at Fallujah and threatened at Najaf is brought to an end before civil power is handed over to a provisional government.