From central Baghdad to America's heartland, the car bomb is now the terrorist's weapon of choice, an urban historian tells Huw Richards.

Almost nightly, television news broadcasts, especially those from Iraq, feature pictures of the charred and twisted remains of automobiles that have been blown up in an urban area, killing and maiming innocents who had been going about their daily business. Across the world, the car bomb seems to be the weapon of choice for insurgents and terrorists.

Most people would prefer not to dwell on such a gruesome feature of modern life, but grim realities are the stock-in-trade of the urban historian Mike Davis. His latest book, Buda's Wagon: A Brief History of the Car Bomb , follows works such as Late Victorian Holocausts , Planet of Slums and Monster at the Door , on the possibility of an avian flu pandemic.

Yet Davis is not himself grim. Somebody cheerless would hardly leaven his tough works with a series of children's books featuring his son as hero.

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Nor, despite occupying a chair at the University of California, Irvine, is he a conventional academic. Now 60, he did not go to university until he was 30, he never completed a doctorate and he has spent some of the time since in the decidedly un-ivory-towerish occupations of labour organiser and truck driver.

Working as "an itinerant lecturer" brought him to the UK in the 1980s. He worked in Belfast and established enduring links with New Left Review and publishers Verso. In the preface to his first and best-known book, City of Quartz (1990), he credits Anthony Barnett - the catalyst for any number of significant developments in British intellectual life - with encouraging him to start work on the history, development and, above all, singularity of Los Angeles.

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It was City of Quartz that enabled his transformation into what he terms "an overpaid college professor" and laid the trail for much that has followed. He identifies two themes in his work. One is a continuing study of Southern California, "a megalopolis of 20 to 25 million people", whose most recent product is Magical Urbanism (2000), a study of the Latino experience in the region. The extent to which Los Angeles was and is shaped by the differing but interrelated trajectories of a diverse population also led naturally to an interest in globalisation and its consequences. Late Victorian Holocausts (2000) was the first of a series on this theme.

Davis says: "I wanted to look at the extreme violence that accompanied the integration of the great subsistence peasantries of India and China into a world economy, which was then controlled from London. It provides a political explanation for great famines that have largely been forgotten or excluded from history - Niall Ferguson, for instance, does not mention them."

There are, he argues, strong parallels with the treatment of the modern proliferating urban poor whose travails he chronicles in Planet of Slums (2006). "You have rapid urban development characterised by the withdrawal or abdication of the state in the provision of housing, medical care and employment." As a consequence, the poor are forced to rely on their own, sometimes desperate devices to survive, and many do not.

Davis's interest in globalisation has in turn generated Monster at the Door and Buda's Wagon . He makes it clear that there is no simple linear progression between urban immiseration and the growth of car bombing. "Many of the people who use car bombs certainly cannot be described as the wretched of the earth." But the existence of a growing number of people who are in effect "expelled from the global economy and have no labour power" certainly favours its continuing proliferation.

Buda's Wagon takes its title from the Italian anarchist Mario Buda, whose Wall Street car bomb of 1920 is reckoned by Davis to be the first - he cites the Royalist attempt to kill Napoleon with a bomb on a cart in 1800 and 19th-century anarchist dreams of destructive "infernal machines" as forerunners. The book carries the hallmarks of his previous works - crisp clarity and a formidable range of sources, academic and otherwise - as it chronicles the apparently inexorable development of the bomb from Buda to Baghdad by way of Saigon, Beirut, Oklahoma City and the attacks on the World Trade Centre on September 11, 2001, which he regards as an airborne variant on the same idea.

Like all books on unpleasant subjects, Buda's Wagon is open to misreading. Davis was nonplussed by a broadcast interviewer's suggestion that he had a romantic view of car bombers. Certainly he believes that "some of the people who have used car bombs - the Basques, the IRA and Hezbollah, for instance - do have legitimate grievances".

He does not, however, believe that the end ever justifies this particular means, which he describes in the book as a "fascist" weapon. "I don't think you can justify a weapon that kills innocent people indiscriminately". He notes that Nelson Mandela rejected it as a weapon during the African National Congress's struggle against apartheid. "He was under pressure to retaliate against state violence, but he recognised that to use a weapon like this would destroy the moral authority that was one of the ANC's great strengths."

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Similarly, Davis cites mainstream Zionist reactions to its use in the late 1940s. "David Ben-Gurion and the Haganah were horrified because they realised that before long it would be used in retaliation against the Jewish population."

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In general, however, it was rare for a group that felt oppressed to reject car bombing. Davis says: "It is like a virus released into the bloodstream.

Once it escapes, it is almost impossible to contain or resist. The temptation for marginal groups is too great."

Car bombs are, he argues, "the poor man's air force". They are, he notes, noisy in the metaphorical as well as in the literal sense, allowing small groups to generate huge publicity and terror. "They destroy their moral credibility but allow them to gain immense leverage."

The technology is available. "It is almost ridiculously simple," Davis says. His account of the University of Wisconsin radicals who learnt of the possibilities of ammonium nitrate fertiliser from a book aimed at farmers who wanted to blast themselves duckponds would be comical but for the ghastly outcome - an innocent physics researcher was killed, others were seriously injured and fresh opportunities were opened for more competent and malevolent groups.

There are, he points out, 3 million trucks of the kind preferred by bombers in the US alone, all of which makes the bomber hard to identify, let alone catch.

Davis argues that this covert element makes it a particularly appealing weapon for secret-intelligence organisations. Davis is not easily shocked, but he says: "I was very struck when I got into my research by the extent to which intelligence services - in particular Israel, India, the CIA in Kabul and, most of all, the Pakistani service - had aided the spread of car bombs." For example, the Pakistani secret service trained the car bombers responsible for 17 blasts that killed 257 people in a single day in Mumbai in 1993.

And he admits to being bemused and horrified by the apocalyptic ideologies and actions of some groups. "One of the things that is shocking about many of the suicide bombs in Baghdad is that they could just as easily be set off by remote control. There is something here that I find unfathomable."

The car bomb is, Davis argues, all but unstoppable, and the terror it spreads has a profound affect on urban life as security measures create would-be exclusion zones and "rings of steel". It will, he fears, become ever more of a threat. "Things won't get better unless you get some reassertion of more traditional forms of resistance or of self-organisation among the poor, and I see no sign of that."

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Buda's Wagon by Mike Davis is published by Verso, ?12.99. It will be reviewed in the issue of April 6.