Lack of intelligence left the US vulnerable to attack at Pearl Harbor
The intelligence failure over Iraq will take a prominent place in the history of notable intelligence breakdowns.
These range, if you want to go back far enough, from the wooden horse in Troy to, in modern times, Stalin's refusal to believe that Germany would invade the Soviet Union in 1941, and the British belief that they would have warning of an Argentine invasion of the Falkland Islands in 1982.
Intelligence also failed to warn against - let alone stop - the two sudden and daring strikes against the US, at Pearl Harbor in 1941 and on 11 September 2001.
Intelligence failures can be put into a number of categories:
This is characterised by a determination to overemphasise information, leading to a false conclusion.
The Senate Intelligence Committee has detailed how this happened over Iraq.
But there is another example of this, which nearly led to disaster in the Cold War.
It is known as Operation Ryan, an acronym for the Russian words raketno-yadernoye napadenie, meaning nuclear missile attack.
Ryan was a KGB operation in the early 1980s, when Ronald Reagan was president.
It was based on a fear that the US was going to launch a missile attack on the Soviet Union.
KGB agents around the world were told to look out for unusual signs of military activity and, of course, found them or said they did.
In their book, KGB: The Inside Story, Soviet defector Oleg Gordievsky and espionage writer Christopher Andrew give a hilarious account of how KGB agents looked out for lights on unusually late in places such as the British Foreign Office.
Fortunately, the West had Gordievsky to warn it about this Soviet state of mind.
Reassuring signals were put out and danger was averted.
This is the syndrome in which the intelligence services or the political leadership completely misread the enemy's intentions.
In 1941, Stalin was apparently convinced that Hitler would not invade the Soviet Union, despite strong military signs to the contrary and urgent warnings from Britain and the US.
Stalin ignored evidence of German intentions to invade
Churchill even passed on some intelligence - gained from the Ultra secret, the reading of the German Enigma codes - that Germany had deployed new armoured formations in southern Poland.
There was also a Soviet spy in Switzerland who sent Moscow the date on which the invasion would start, 22 June.
Stalin did not want to know.
To this day, nobody really knows why.
This category is closely linked to the next.
Here, one side is so confident of its ability that it projects its reasoning onto the other side and believes that since it would not do something itself, nor will the other side.
The classic case is the Yom Kippur war of October 1973.
The Israelis had what was called the "concept" - Egypt could not win a war, so it would not start a war.
In fact, Egypt had the more limited aim of establishing a bridgehead across the Suez Canal and converting this into a diplomatic victory. It did so.
The Israeli commission of inquiry was highly critical of the "concept", and Prime Minister Golda Meir resigned.
This happens when you know the enemy might do something, though you are not sure what or when, and yet you do nothing anyway.
The British suffered from this over the Falkland Islands in 1982.
Britain had to fight to regain the Falkland Islands
The Argentine military junta had made it clear that it wanted to gain sovereignty.
Yet even when negotiations stalled in early 1982, Britain did nothing to prevent an invasion.
The British ambassador in Buenos Aires called it the Micawber policy after the Dickensian character who hoped that something would "turn up".
What turned up was the invasion of the islands and a bloody little war.
However, an inquiry by Lord Franks, a former diplomat, said the government was not to blame because the Argentines had acted unpredictably.
Something similar happened when Saddam Hussein invaded Kuwait in 1990.
People thought he might do so, but hoped he would not and did nothing.
On the whole, it is as well to fear the worst when a dictator makes threats and moves armies.
When there is virtually no intelligence, you are at the mercy of events.
While it is the case that there were signs in 1941 of aggressive Japanese intentions towards the US, nobody in a senior position expected the attack on Pearl Harbor.
It was carried out with skill and surprise.
But ignorance should not lead to inaction.
The US Congress issued a stinging report because no adequate steps were taken in Pearl Harbor itself to cover against an attack.
Although the radar station picked up the approach of the Japanese aircraft, nobody could interpret the signs and there were no aircraft ready to repel them.
Failure to join the dots
This is the failure to make connections between bits of intelligence to make a coherent whole.
It is more easily identified afterwards than at the time.
One of the main charges against the CIA and FBI post-9/11 was that they failed to join up the dots beforehand - the presence in the US of known suspects, the unusual number of men from the Middle East taking flying courses, the known tactic of al Qaeda to use aircraft, etc.
Finally, a word about that wooden horse.
The key intelligence failure was that the Trojans ignored a warning.
It came from Cassandra, the daughter of Troy's King Priam.
Given the gift of prophecy, she had then angered the God Apollo, who ordained that her prophecies should never be believed.
So the Trojans rejected what they said was her "windy nonsense".
A myth perhaps, but there is a lesson to be learned.
The trouble is that lessons are not always learned, which is why the list of intelligence failures grows longer.