Within hours of the attacks on the World Trade Centre in New York and the Pentagon building in Washington, the finger of suspicion pointed at Osama bin Laden, the Saudi militant believed to be living in Afghanistan who has been the United States' most wanted man for at least three years.
Senior intelligence officials briefing members of Congress said the attacks bore the "fingerprint" of Mr bin Laden, who is also suspected of masterminding the 1998 attacks on the US embassies in Nairobi and Dar es Salaam, and the bombing of the USS Cole in Aden harbour in Yemen last October.
The intelligence briefing was made public by the Republican Senator Orrin Hatch and others. "Who else would have the capability to co-ordinate the simultaneous hijacking of several aircraft?" a Federal Bureau of Investigation official, speaking on condition of anonymity, told the Los Angeles Times.
US officials see Mr bin Laden as someone who specialises in co-ordinated attacks involving a highly secret, highly efficient, highly dedicated network of guerrilla fighters willing to lay down their lives for their cause. Officially, the White House remained open to the possibility of other perpetrators, including domestic ones, but only one man and his organisation were being considered with any seriousness.
Whoever carried it out mastered some astonishingly complex logistics: getting teams of hijackers on to four separate flights at three different airports, Logan in Boston, Dulles in Washington and Newark, New Jersey. All of them had to skirt airport security, either by carrying no weapons at all or by carrying ones that would escape detection by metal detectors.
According to Barbara Olson, the wife of the US Solicitor General who was on the plane taking off from Dulles that ended up slamming into the Pentagon, the attackers herded the passengers into the back of the plane wielding what looked like knives and cardboard cutters. Mrs Olson called her husband twice by mobile phone before her plane crashed.
Security experts further speculated yesterday that each hijacking team would have included a trained pilot, since no commercial pilot was likely to agree to plough into a building.
The growing certainty about Mr bin Laden raised the possibility of a retaliatory strike, alluded to by many senior Bush administration and congressional officials. It also raised questions about the competence of US intelligence-gathering in tracking and preventing this kind of assault.
Administration officials insisted they had received no credible threat warning them of the attacks. But a senior intelligence official told the Los Angeles Times: "We're just amazed at the level of coordination this would have taken. And the more extensive the conspiracy, the more opportunity US agencies should have had in picking up some trace this was going to occur ... You're only as good as the intelligence you have, and in this case, intelligence failed us."
At least one report suggested Mr bin Laden had warned three weeks ago that he was about to carry out an "unprecedented" attack against the US as punishment for its support for Israel in the Middle East conflict. "We received several warnings like this," Abdel Bari Atwan, editor of the London-based Al Quds Al Arabi weekly news magazine, told Reuters.
Mr Goss conceded there would have to be a major rethink of how terrorist threats are dealt with. Lee Hamilton, a former congressman from Indiana and a noted foreign and security policy expert, said he expected major new funding to bolster America's intelligence network, a review of foreign and security policy and a close look at the workings of the FBI and CIA. "There will be very profound consequences for years and years to come," he said.
Before yesterday, the worst act of terrorism on American soil was home-grown: the bombing of the federal building in Oklahoma City in 1995, killing 168 people. The last major outrage from a foreign source was the 1993 truck bombing of the World Trade Centre, in which six people died and 1,000 were injured.
That attack in many ways foreshadowed yesterday's. Ramzi Yousef, held to be the mastermind of the 1993 assault who is now serving a life imprisonment, was believed to have planned to topple one of the Centre's two towers into the other, and to release a cloud of deadly cyanide gas. He failed in that aim – the bomb was not powerful enough, and the gas evaporated in the heat of the explosion. He was caught before he could carry out another plan, to blow up 11 US commercial aircraft in one day.
Mr bin Laden, meanwhile, has eluded attempts either to capture him or to assassinate him. Now living in Afghanistan, which is under the hardline Islamist rule of the Taliban, he has made numerous public statements threatening renewed attacks on the US.
Two weeks ago, Indian police accused Mr bin Laden of plotting to bomb the US embassy in New Delhi. And 10 days ago the intelligence services of Britain, Israel and the US were alerted when one of the passengers on a plane which crash-landed at Malaga airport turned out to be a suspected bagman for Mr bin Laden. They lost him after he was released from hospital where he received treatment for minor injuries.
The name of Osama bin Laden also cropped up in connection with a failed plot to blow up Los Angeles airport. Ahmed Ressam, an Algerian, was stopped with explosives in his car as he tried to cross into the US from Canada in 1999.Reuse content