Until very recently, most suicide bombers were secular in origin. The techniques of suicide bombing were first developed by the Tamil Tigers, a Marxist-Leninist group operating in Sri Lanka that recruits mainly from the island's Hindu population, but which - like Marxist-Leninist parties everywhere - has always been intensely hostile to religion. Until 2003, the Tigers were responsible for more suicide bombings than any other single organisation in the world, including Hamas and Islamic Jihad. Communists and socialists were responsible for most of the suicide bombings that occurred in Lebanon in the early 1980s, forcing the withdrawal of US and French forces. More than a third of the suicide bombings committed by Muslims between 1980 and 2003 were the work of members of secular groups such as the Kurdistan Workers' Party. The situation changed with the invasion of Iraq. Until that time suicide bombing had been unknown in that country. Since then, there have been more suicide bombings in Iraq than in any other part of the world, many of them carried out by Islamists. Yet their principal objective is to drive US and allied forces out of the country, a goal shared by Ba'athist forces left over from Saddam Hussein's secularist regime.
The practice of suicide bombing originated in secular movements with specific political goals, and even where it attracts Islamist militants it is employed chiefly to advance a definite political agenda. This is the conclusion of Robert Pape's recent book Dying to Win: the strategic logic of suicide terrorism, the most rigorous empirical study of the phenomenon to date. Pape argues that suicide bombing is a rational strategy. It has no essential connection with religion. Viewed as part of what military theorists call asymmetric conflict - the struggle of the weak against the strong - suicide bombing is a cheap, highly focused and devastatingly effective technique of warfare. It worked in Lebanon, and it seems to be working in Iraq.
Pape's analysis does an enormous service in showing that what many view as the most senseless behaviour can be understood in rational terms, but that terrorism - even suicide terrorism - is not a simple phenomenon. People take part in it for a variety of reasons, and thinking of suicide bombing solely as a technique of armed struggle risks missing its role in giving meaning to the lives of the bombers. Becoming a suicide bomber may be a strategic decision in Baghdad, but the disoriented young men who carried out the 7 July attacks in London seem to have had no clear objectives, just an overwhelming sense of alienation from society. For them, becoming suicide bombers may have been a refuge from anomie, the feeling of purposelessness that has often fuelled the growth of cults.
In Perfect Soldiers, Terry McDermott seeks to uncover the motives of the 11 September 2001 hijackers. Who were they, how did they come together and - above all - why did they do what they did? McDermott aims to answer these questions by giving as full an account of the events leading up to the attacks as can be pieced together from the sources currently available. The result of his efforts, involving years of investigation using sources from all over the world, is a powerful narrative that presents the most convincing picture of the 9/11 hijackers to date.
In the media, terrorists are often portrayed as dysfunctional human beings, but McDermott demonstrates that there is no distinctive terrorist psychological profile. The hijackers had very different personalities, and most were remarkable for their ordinariness. Mohammed Atta, the pilot of the first plane to hit the World Trade Center, was an anxious and puritanical individual, but the pilot of the second plane, Marwan al-Shehhi, who seemed strict and withdrawn when he first arrived in Germany, soon emerged as an "easygoing, robust, hail-fellow-well-met young man who loved to sing and laugh". Ziad al-Jarrah (who piloted the plane that crashed in Pennsylvania) was a handsome young man from a thoroughly secularised middle-class family. He married a lively Turkish student with whom he seems to have been, for a time, genuinely happy. The pilot of the plane that crashed into the Pentagon, Hani Hanjour, was a "meek and quiet" person who worked hard to get his flying licence but found difficulty getting a job, and spent a lot of time surfing the internet.
These are not the demoniacal psychopaths of media legend, but average types, with an unexceptional range of traits and problems, yet they ended up mounting an attack that claimed the lives of nearly 3,000 innocent people. As McDermott shows in a meticulous reconstruction, their involvement in terrorism was not the result of a single decision but the end point of a long period of drift. Ziad al-Jarrah came from a secular Muslim background, but along with a number of others who turned to terrorism, he converted to a cultish version of Islam in Hamburg. No doubt opposition to western policies was a crucial factor in this conversion, but so were the psychological benefits the converts gained. McDermott writes that they "chose not simply a new mosque or religious doctrine but an entry to a new way of life, the acquisition of a new world-view, in fact, of a new world". For these men, becoming jihadists - not in the sense in which jihad refers to the believer's struggle for his own soul, but rather that in which it enjoins incessant struggle against unbelievers - resolved a chronic existential crisis. From being drifters, they became warriors.
It is natural to look for a rational explanation of terrorism. How else can we hope to control it? But human behaviour is often irrational, and suicide bombing does not always have well-defined political ends. Sometimes it is more like behaviour of the kind that occurred in Jonestown, Guyana, where more than 900 people committed mass suicide in 1978. History is full of such apocalyptic movements, not all of them religious: many Nazis and communists were ready to kill and die in order to destroy the existing order of things. By doing so, they injected a kind of meaning into their lives, and it is hard to resist the suspicion that it is the same need that drives some suicide bombers.
Terrorism of this apocalyptic variety cannot spread unless there is a wider sense of grievance against the world, but it is not the work of ice-cold strategists. The ends it serves are inchoate, and it can be extremely amateurish in execution. McDermott notes that Ramzi Yousef - the "terrorist mastermind", also known as Abdul Basit Karim, who organised the 1993 attack on the World Trade Center - was so casual and disorganised in his methods that a CIA official described him as an "ad hoc terrorist". Yousef had only the vaguest and most unrealistic political demands, and the Liberation Army he claimed to represent was a figment of his imagination. Yet his attack killed six people and injured a thousand more. Ad hoc terrorism is a serious business, but it does not require a special sort of person to engage in it. With the right background of grievance and alienation, anyone can join in.
John Gray's most recent book is Al-Qaeda and What It Means to Be Modern (Faber & Faber)