Looking back at the 13 attacks that have killed 131 people in Israel since April 1994, a portrait of the suicide bomber begins to emerge. He is a young man, between about 19 and 25, and comes from a very devout Muslim family He is unmarried, usually a middle child of 10 or 11 (and so not the principal wage earner). Most are from refugee camps, usually in the Gaza Strip.
And the bombers are the children of the intifada. Many lost fathers or brothers in clashes with Israeli soldiers; most had been held in Israeli jails without charge for months at a time. Arrests and beatings were their main, perhaps only, experience of Israel.
Salah Shaqqer, for example, carried a bomb which killed 21 Israelis at a bus stop in Beit Lid in Israel in January 1995. Aged 25, he was from Yebna Refugee Camp in the Gaza Strip, and worked as a nurse. He was wounded by Israeli gunfire on six separate occasions during the intifada, had been held without charge for three months and was allegedly tortured by his Israeli interrogators.
Ahmed Saif, a Palestinian journalist who has studied the bombers extensively, said the common thread running through their lives was hopelessness. "They are too poor to study, they can't find work, and they really believe there is no future for them in this life, or in this country." In almost every case, if the bomber himself did not grow up in a refugee camp, he came from a family of refugees, and had a strong awareness of the Palestinians' lost birthright.
Recruiters from Hamas or Islamic Jihad, says Mr Saif, look for youths who hunger desperately for the riches they are told await a martyr in heaven. Hamas is active in the most squalid camps, like Fowwar, and boys learn early of the rewards of martyrdom from activists who incorporate doctrine into the plays and sporting events they organise - often the only recreation.
"Hamas is not a military organisation. It's a political party," explains Ziad Abu Amr, a political scientist and Islamic expert. "It has the infrastructure of a large party, including the military wing. But it also has a social welfare wing, which provides schools, medical services and day-care centres. Accordingly, Hamas has a large base of popular support, especially among the poor."
In recent years, Hamas has also increased its support among secular and middle-class Palestinians, who see it as the only voice still advocating resistance to a peace process that has not brought the freedom promised.
Founded in 1987 in Gaza, an offshoot of the Muslim Brotherhood in Egypt, Hamas - the Arabic acronym for the Islamic Resistance Movement - is considered more nationalist than Islamist. While the goal of the Muslim Brotherhood is the establishment of an Islamic state, Hamas is more a liberation movement in the mould of Hizbollah (The Party of God) in Lebanon. But to support Hamas is not, Dr Abu Amr notes, necessarily to support bus bombings. He estimates that Hamas, in all its activities, has a core of support from 20 per cent of Palestinians in the territories, while the rest of their support fluctuates.
"It depends on the performance of the Palestinian Authority, and its ability to deliver for its people," he says. "It also depends on the policies of Israel, on closures of the occupied territories, on the expansion of Israeli settlements and on the punishment of Palestinians."
The recent series of suicide bombings has raised questions about a split within the movement. The Iz a-Din al-Qassam Brigade, which claimed three of the bombings, is only a small part of Hamas. Hours after the first two attacks, the Qassam Brigade's leadership issued a leaflet in Gaza, offering Israel a three-month truce, but exactly a week later there was another bomb. While Qassam claimed that attack as well, the initial news of the bomb caused consternation among the local leadership.
The first bombings were seen by many as an attempt by Hamas to avoid political marginalisation in the wake of the Palestinian elections (which it boycotted). The third attack was less easy to explain. Was it the Hamas leadership abroad affirming its role - or a group of young mavericks? Despite a torrent of leaflets issued since, the movement's goal, and who is responsible for its actions, remain unclear.