Mr Osama bin Laden's al-Qa'ida movement is considered by US analysts to be the most likely culprit for yesterday's terrorist attack on New York City and Washington, DC.
Although a spokesmen for al-Qa'ida, "The Base", and the Afghan Taliban, who give Mr bin Laden refuge, denied responsibility for the hijackings and bombings, he will remain the leading suspect until he is found innocent of involvement.
While al-Qa'ida has not previously mounted an operation of this scale or sophistication, there is no doubt that the movement has a global reach through the vast network of deeply disaffected veterans of the Afghan war (1979-1991). Arab and Muslim fighters, known as "Mujahedin", were recruited from Middle Eastern and South Asian countries to fight the Soviet-backed government in Kabul. The Mujahedin were trained in camps in Pakistan by Pakistani military intelligence and the US Central Intelligence Agency. The prolonged campaign was largely funded by Saudi Arabia.
After the Soviet withdrawal from Afghanistan, some of the thousands of Mujahedin joined the Afghan warlords who carried on a seemingly unending civil war. Others, who became known as "the Afghans", went back to their home countries or became freelancers in what could be called the "Islamic International Brigades", the "Azzam Brigades". According to the authoritative Jane's Intelligence Review, "the Afghans" loosed onto the international scene included 5,000 Saudis, 3,000 Yemenis, 2,000 Egyptians, 2,800 Algerians, 400 Tunisians, 370 Iraqis, 200 Libyans and scores of Jordanians. They have taken part in the Bosnian war and the Kosovo campaign as well as various civil conflicts in the Muslim world, particularly the Islamist insurrection against the secular government in Algeria.
Mr bin Laden was born in 1957 into a prosperous Saudi family involved in the construction business. He joined the Mujahedin in 1979 soon after the Soviet Union invaded Afghanistan and became one of their most celebrated fighters.
He also put his wealth behind the struggle. He recruited hundreds of Arab volunteers to the training camps and the battlefield. He armed them and supported the campaign by blasting massive tunnels for hideouts, command centres and arms dumps into the mountains of Bakhtiar province. His engineers cut a guerrilla trail across the country to the vicinity of Kabul.
Once the fundamentalist Taliban took power in Afghanistan, Mr bin Laden based himself in the country. He became the world's most wanted fugitive in 1998 when his agents bombed the US embassies in Dar es-Salaam, Tanzania, and Nairobi, Kenya.
He has been associated with the attack on the USS Cole in the port of Aden in October 2000 and with the so-called "millennial bombing conspiracy" uncovered when an Algerian, Mr Ahmad Rassan, was detained while entering the US in a car containing bomb-making materials. Mr Bin Laden has also been linked with failed plots against US embassies in New Delhi and Aden.
Mr bin Laden has repeatedly issued declarations of jihad or "holy war" and fatwas or "religious rulings" against the US because of its support for Israel and for pro-Western Arab governments he deems to be "anti-Islamic", including the Saudi monarchy, which he aims to overthrow and replace with a truly "Islamic" regime like that of the Taliban in Afghanistan. His popularity in Arab and Muslim countries soared after the attack on the USS Cole which coincided with the beginning of the second Palestinian uprising, the intifada, against Israeli occupation.
Although Mr bin Laden is the prime suspect, it is not known whether his followers have the competence to mount such a major terrorist offensive. The 1991 bombing of the World Trade Centre, masterminded by Mr Ramzi Yusif, a member of the "Afghans", was a minor operation compared with yesterday's outrage. The only Middle East group which once had the capability to stage multiple civilian aircraft hijackings was the Popular Front for the Liberation of Palestine (PFLP). The PFLP was the first Palestinian guerrilla group to hijack a plane in 1969. The PFLP, and the breakaway Democratic Front, promptly denied responsibility for yesterday's onslaught.
Other Islamic groups besides al-Qa'ida have recruited "Afghans" into their ranks. These include: Al-Gama'at al-Islamiya, the Egyptian Islamic organisation, which surfaced in 1997 and was responsible for several attacks in Egypt, including the 1997 attack on tourists in Luxor in which 62 died; the Aden Islamic Army, said to be linked to Mr bin Laden, which has claimed up to 20 bomb attacks in southern Yemen as well as the kidnapping of foreign tourists; Al-Jihad, the Egyptian branch of Islamic Jihad, which assassinated Egypt's president Anwar Sadat in 1981.
Arab groupings opposing Israel - such as the Lebanese Hizbullah movement and the Palestinian Hamas, Islamic Jihad and Abu Nidal organisations - do not have the following or the ability to stage such an operation.
While ordinary Arabs are disillusioned with the failure of the Western powers, particularly the US, to curb Israel's military campaign against the Palestinians, no Arab or Palestinian contacted by The Irish Times supported yesterday's all-out attack on the US. Indeed, they were horrified by it.