Out went the cover showing Saddam Hussein firing a rifle in the air. In came a photograph of a graveyard packed with the victims of sectarian suicide bombings and festooned with flags and posters showing the bearded and turbaned features of some of the country's new movers and shakers - who were virtually unknown in 2002, the cut off point for the last edition.

Tripp, an Arabist and professor of politics at London University's School of Oriental and African Studies (Soas), is in the vanguard of western scholars of Iraq. He first visited in the 1980s during the war with Khomeini's Iran. To his regret he has not been back since the US-led invasion - neither wanting to worry his family, get stuck and out of touch in Baghdad's Green Zone or be a "hideous liability" to his Iraqi friends. But he has followed events closely - and, crucially, unlike so many of those involved in the war and occupation - against the indispensable background of what came before.

"There was this nonsensical idea that Saddam and everything he created was a kind of freak and that once you eradicated him the whole thing would fall apart and the potential for a liberal, democratic and a civil society would emerge as if somehow he was the only problem," he says. "But Saddam was a recognisable part of Iraqi history. Many Iraqis feel now that they've been delivered into the hands of many lesser dictators. As one of my friends said: 'Thanks very much: you got rid of one Saddam and you left us with 50.'"

Tripp is scholarly and quietly-spoken but there is no ivory-tower reticence about his analysis. The US had "up to date, unprejudiced and non-ideological" experts in the CIA, state department and the academic world, but politicians who listened to out-of-touch Iraqi exiles pushing their own agenda cut them out of the loop. Post-war planning, such as it was, was taken over by the Pentagon.

Part of the problem, he argues, was profound ignorance about what went on beneath the surface of Saddam's dictatorship, what he calls a "shadow state" that ran on cooption, collaboration and patronage as well as repression and fear. That led to the disastrous decision to outlaw the Ba'ath party. "Lack of understanding on that score was unbelievable. By purging it you alienated tens of thousands of people who would otherwise have very happily served the next regime. They weren't going to work for the restoration of Saddam Hussein.

They only joined the Ba'ath because that was what they had to do. When you decapitate that shadow state you don't get rid of the old networks. They just look for a new patron: hence the resistance."

The same "blindness", as Tripp calls it, was at work when the order came to dissolve the Iraqi army and the entire security apparatus of the old regime, giving a huge boost to what was to become a fully-fledged Sunni insurgency.

Tripp and handful of other UK academics had their own taste of the uneasy relationship between knowledge and power at a meeting in Downing Street as the war drums beat louder in November 2002. He had the impression that Jack Straw, the foreign secretary, wanted to inject a little informed scepticism into Tony Blair's thinking. But the prime minister, he recalls, seemed detached except to seek confirmation that Saddam was "uniquely evil". There was little interest in the "hideous complications" - such as religious nationalists and Islamists who might not take kindly to foreign occupation - that might follow.

"We were arguing that removing dictatorship and opening the space for populist politics might produce something that you would find very, very difficult to deal with. I wouldn't say that we predicted civil war and sectarianism of the kind that has emerged, but we were trying to say that there was a complex society in Iraq which shouldn't be reduced to the caricature of Saddam Hussein sitting upon the oppressed masses. The oppressed masses have their own agenda - and sometimes they're very nasty indeed."

The result has been the spread of local centres of power, whether in Basra, Kurdistan or Anbar province, where Sunni tribal sheikhs have mobilised to fight al-Qaida - part of what General David Petraeus, the US commander in Iraq, this week called "Iraqi solutions to Iraqi problems". These developments, suggests Tripp, were an inevitable retreat from the ambitions of US neocons that bore no relation to Iraqi reality. "If you can't read a society like that, you're doomed," he insists. "You'll get it wholly wrong. If the security conditions are so bad you can't create the material inducements for people to come on board, then you have to deal with those who can guarantee a minimum of order and deal with you without trying to attack you."

Iraq's post-war elections and the "formal trappings of constitutional and democratic government," Tripp writes, were "little connected to the life-and-death struggles that formed the texture of a much more local, violent and communal politics." And against the background of the country's new brutalities, he gloomily predicts: "There is a strong possibility that newly-won privileges will be entrenched and Iraqis will have good reason to fear subjection once more to a regime that equates power with force and dissent with treason."

· A History of Iraq, Charles Tripp, Cambridge University Press, Third Edition

· Ian Black is the Guardian's Middle East editor