What President Bush last week called "the first war of the 21st century" began nearly a decade ago, when terrorists converged on New York City with a plan to blow up the World Trade Center.

The February 1993 explosion in the center's parking garage, which killed six people, sketched the first rough outlines of a new kind of terrorism that emerged as a finished portrait last Tuesday with the annihilation of the New York landmark and the deaths of thousands.

As the United States moves to retaliate for the horrific assault and fight a war different from any in its history, it faces an enemy that over the past eight years has grown in confidence, experience and ability. Learning from mistakes and adapting to the West's incomplete successes against it, the new terrorism has evolved to match flexible means with uncompromising goals.

A defining characteristic of the movement's development has been its success in combining a conservative interpretation of Islam and a comfort with aspects of the modern world that have given birth to a highly mobile, popular, wealthy, technologically savvy international enterprise.

An overriding mission

Today, these elements are focused on an overriding mission, expressed concisely in 1998 by Osama bin Laden, the Saudi expatriate who has come to personify the movement. "To kill Americans and their allies — civilians and military — is an individual duty for every Muslim who can do it in any country in which it is possible to do it," he said.

Bin Laden, who U.S. officials have said is the prime suspect in last Tuesday's attacks, is widely considered the architect of the new terrorism. With followers around the world, he is believed to draw on what James Steinberg, who was deputy national-security adviser to President Clinton, called "a network of more or less affiliated organizations, some loosely, some very close."

The groups that form this network allied with bin Laden's organization, known as al Qaeda ("the base"), are concentrated in the Middle East but include members in the Balkans, Chechnya, Southeast and Central Asia, Africa and the United States. They share resources and expertise, lending operatives for particular ventures. They have become, in a sense, models of globalization.

One of the most striking innovations of bin Laden's brand of international terrorism has been a vision of a holy war, or jihad, that excludes any possibility of compromise. Its goal is not to negotiate with the West, as was the case for Palestinian extremists in the 1970s and '80s, but to destroy it.

Bin Laden and his followers do not seek political advantage in a negotiating process. According to Daniel Benjamin, director of the office of transnational threats in the Clinton White House: "They want change that is so radical as to defy any concept of negotiations. ... They are conducting a war, not seeking entrance into the status quo.

"These guys want to roll back 1,300 years of history," said Benjamin, now a senior fellow at the Center for Strategic and International Studies in Washington. "They believe that their violence is divinely justified and that great goals require dramatic means, and the dramatic means is mass bloodshed."

Brian Jenkins, a terrorism expert for Rand, said that because the new terrorists do not respond to political constituencies in the traditional sense, they are "freed from ordinary constraints of morality. ... There is less inhibition to kill in quantity and a greater willingness to die in the process."

Reaching a broader audience

While developing an absolutist view of the struggle with the West, bin Laden has tailored his message in recent years to reach a broader audience of disgruntled and dispossessed people across the Islamic world. No longer does he concentrate only on his founding aim of expelling U.S. forces from the Arabian peninsula, where he believes they defile holy sites of Islam. Instead, he reaches out to Muslims with grievances from Bosnia-Herzegovina to Indonesia.

This broader message has complemented the development of a wider geographic network. Elements in the pan-Islamic coalition range from the Taliban Islamic fundamentalists now ruling most of Afghanistan, where bin Laden has been headquartered since 1996, to Chechens fighting against Russia to Palestinians fighting for an independent homeland.

Groups identified with al Qaeda now operate in about three dozen countries. Alleged participants in bin Laden-inspired plots — from the bombing of U.S. embassies in Kenya and Tanzania in 1998 to plans to disrupt millennium celebrations in the United States in the first hours of 2000 — have included citizens from dozens of countries, including Saudi Arabia, Algeria, Jordan, Pakistan, Malaysia and the United States.

The emphasis on America as a common enemy is a unifying principle for this far-flung association. In bin Laden's view, the United States "heads the list of aggressors against Muslims."

In a 1998 ABC News interview, bin Laden compared his war against America with the struggle to expel Soviet invaders from Afghanistan during the 1980s, which was a seminal experience for him and many of his followers. "Our battle against the Americans is far greater than our battle was against the Russians," he said. "We anticipate a black future for America. Instead of remaining United States, it shall end up separated states and shall have to carry the bodies of its sons back to America."

Stature, money and support

Even as al Qaeda has grown and come under increasing pressure from the United States and its allies, it has demonstrated resilience stemming from bin Laden's growing stature in the Islamic world, his inherited fortune — estimated at as much as $300 million — and a broad base of support.

Wealthy individual sympathizers and clandestinely supportive governments channel money into what Stephen Phillip Cohen, a South Asia expert and former State Department official, described as an international fund for Islamic terrorists.

"The money comes from a lot of countries," Cohen said, "often under pretext of helping freedom fighters in Palestine and Kashmir ... and some of it goes to bin Laden. He's sort of the Ford Foundation of terrorists," providing support for projects he considers worthy.

Some operations in recent years linked to bin Laden have appeared to need little outside financing, relying on credit-card fraud and other criminal activities.

Several of the terrorist hijackers who U.S. officials say piloted the doomed commercial aircraft in last Tuesday's attacks appear to have been well-funded, paying $10,000 each for flight school, living in middle-class neighborhoods and spending significant amounts on apartment and automobile rentals, restaurants and clothes.

For some terrorism experts, the high level of funding is even less notable than the accomplished profiles of the suicide bombers in the attacks. While classic suicide bombers have tended to be uneducated and inserted into a plot at the last moment by their handlers, the terrorists in this attack were in some cases university-educated people who had prepared for their mission for months, even years.

"The assumption (among Western terrorism experts) was that the average suicide bomber was a psychologically damaged 19-year-old with a limited education," said Jenkins, the Rand expert. "These people were ... leading normal lives with wives, taking the garbage out, taking kids to McDonald's, taking flying lessons, living in comparatively pleasant places, all the while knowing that on some date they were going to kill themselves and thousands of people."

According to Steven Emerson, who has looked at Islamic groups in the United States for the Washington-based Investigative Project, al Qaeda has been active in the United States since the early 1990s, growing out of fund-raising efforts for Afghan and Pakistani refugees, recruiting U.S. citizens.

A borderless trend

The international, borderless nature of al Qaeda is a radical departure. "The larger trend has been away from state sponsorship, toward nonstate terrorism," said Paul Pillar, CIA national intelligence officer for the Near East and South Asia, and former deputy director of the agency's counterterrorism office.

This wasn't always the case for bin Laden, nor is it entirely true today. Throughout his 20-year career as a jihadist, bin Laden has always depended on a certain degree of state support, or at the very least state tolerance, starting with his membership in the anti-Soviet rebel force in Afghanistan — a movement that received about $2 billion in covert U.S. funds.

During the early 1990s, bin Laden enjoyed the protection of the Islamic government of Sudan. Since his expulsion from Sudan in 1996, he has relied on support from the Taliban rulers of Afghanistan. In return for sanctuary, he has given the Taliban money and fighters to consolidate their hold over the country.

Bin Laden also reportedly has received indirect support from Pakistan, whose secret services have used the Taliban and Islamic jihadists as proxies for carrying out a guerrilla struggle against India in Kashmir. There are training camps for jihadists in Pakistan, as well as in Afghanistan, training students from places as far apart as Chechnya, Uzbekistan, Yemen, Kuwait and Bangladesh.

More controversial are allegations of links between bin Laden and Middle Eastern states such as Iraq and Iran. The 1998 indictment of bin Laden by a federal grand jury in New York alleged that al Qaeda had "reached an understanding" with the Baghdad government to work cooperatively on certain projects, such as weapons development, but this was never proved.

Bin Laden and Iraqi leader Saddam Hussein share one obvious goal: the expulsion of U.S. troops from the Middle East, particularly Saudi Arabia. But the trial evidence also revealed that some al Qaeda operatives distrusted Saddam, whom they considered "a bad Muslim."

Much of what U.S. intelligence knows about how bin Laden and al Qaeda operate has come from documents captured during anti-terrorist operations or from arrested terrorists looking for leniency.

Jamal al Fadl, an al Qaeda defector who testified in the trial of four men convicted in the 1998 embassy bombings, illuminated an organization structured with bin Laden and his consultative council at the top, surrounded by committees to handle business enterprises, military training, religious policy and even publicity.

Other testimony from insiders revealed that al Qaeda communicated with embassy-plot participants via a satellite telephone purchased in New York, and subpoenaed phone records helped tie bin Laden to the bombings. An al Qaeda training manual captured in a raid in California revealed other secrets about the group.

Learning from mistakes

Yet this knowledge, much of it revealed in open court, has had an ironic effect, specialists said. From each setback represented by an arrest and trial, bin Laden and his associates have been granted an inside view of how U.S. authorities are pursuing al Qaeda.

"Every success contributes to the next failure," former Clinton adviser Steinberg said. "We've had to blow every investigative and intelligence technique. ... Every time you have to go to court and do it, it's like handing over the investigation manual to the other guys. They see every place where they screwed up."

Al Qaeda has a proven talent for knowing when to move on. Since last Tuesday, the whole world has learned that some of the participants in last week's attack had been receiving pilot training at U.S. flight schools. Plotters of any future operation are unlikely to choose the same path.

"The terrorists will go elsewhere," said James Lindsay, a former National Security Council director of global issues and multilateral affairs.

"They look for the places where you are vulnerable and attack you there, when they can catch you flat-footed. They are always looking for the places where you're not looking. They study you."