Osama bin Laden, who was killed in Pakistan on Sunday, was a son of the Saudi elite whose radical, violent campaign to recreate a seventh-century Muslim empire redefined the threat of terrorism for the 21st century.

With the attacks on the World Trade Center and the Pentagon on Sept. 11, 2001, Bin Laden was elevated to the realm of evil in the American imagination once reserved for dictators like Hitler and Stalin. He was a new national enemy, his face on wanted posters, gloating on videotape, taunting the united states and western civilization.

“Do you want bin Laden dead?” a reporter asked President George W. Bush six days after the 9/11 attacks.

“I want him — I want justice,” the president answered. “And there’s an old poster out West, as I recall, that said, ‘Wanted: Dead or Alive.’”

It took nearly a decade before that quest finally ended in Pakistan with the death of bin Laden during a confrontation with American forces who attacked a compound where officials said he had been hiding.

The manhunt was punctuated by what culminated in a December 2001 battle at an Afghan mountain redoubt called Tora Bora, near the border of Pakistan, where Bin Laden and his allies were hiding. Despite days of pounding by American bombers, bin Laden escaped. For more than nine years afterward, he remained an elusive, shadowy figure frustratingly beyond the grasp of his pursuers and thought to be hiding somewhere in Pakistan and plotting new attacks.

Long before, he had become a hero in much of the Islamic world, as much a myth as a man — what a longtime officer of the Central Intelligence Agency called “the North Star” of global terrorism. He had united disparate militant groups, from Egypt to Chechnya, from Yemen to the Philippines, under the banner of his al Qaeda organization and his ideal of a borderless brotherhood of radical Islam.

Terrorism before bin Laden was often state-sponsored, but he was a terrorist who had sponsored a state. For five years, 1996 to 2001, he paid for the protection of the Taliban, then the rulers of Afghanistan. He bought the time and the freedom to make his group, al Qaeda — the name means “the base” — a multinational enterprise to export terror around the globe.

For years after the September 11 attacks, the name of al Qaeda and the fame of bin Laden spread like a 21st-century political plague. Groups calling themselves al Qaeda, or acting in the name of its cause, attacked American troops in Iraq, bombed tourist spots in Bali, and blew up passenger trains in Spain.

To this day, the precise reach of his power remains unknown: how many members al Qaeda could truly count on, how many countries its cells had penetrated, and whether, as bin Laden boasted, he sought to arm al Qaeda with chemical, biological and nuclear weapons.

He waged holy war with distinctly modern methods. He sent fatwas — religious decrees — by fax and declared war on Americans in an e-mail message beamed by satellite around the world. Al Qaeda members kept bomb-making manuals on CD-ROM and communicated with encrypted memos on laptop computers, leading one American official to declare that Bin Laden possessed better communication technology than the United States. He railed against globalization, even as his agents in Europe and North America took advantage of a globalized world to carry out their attacks, insinuating themselves into the very western culture he despised.

He styled himself a Muslim ascetic, a billionaire’s son who gave up a life of privilege for the cause. But he was media-savvy and acutely image-conscious; before a CNN crew that interviewed him in 1997 was allowed to leave, his media advisers insisted on editing out unflattering shots. He summoned reporters to a cave in Afghanistan when he needed to get his message out, but like the most controlling of C.E.O.’s, he insisted on receiving written questions in advance.

His reedy voice seemed to belie the warrior image he cultivated, a man whose constant companion was a Kalashnikov rifle that he boasted he had taken from a Russian soldier he had killed. The world’s most threatening terrorist, he was also known to submit to frequent dressings down by his mother. While he built his reputation on his combat experience against Soviet troops in Afghanistan in the 1980s, even some of his supporters question whether he had actually fought.

And though he claimed to follow the purest form of Islam, many scholars insisted that he was glossing over the faith’s edicts against killing innocents and civilians. Islam draws boundaries on where and why holy war can be waged; Bin Laden declared the entire world fair territory.

Yet it was the United States, Bin Laden insisted, that was guilty of a double standard.

“It wants to occupy our countries, steal our resources, impose agents on us to rule us, and then wants us to agree to all this,” he told CNN in the 1997 interview.

“If we refuse to do so, it says we are terrorists. When Palestinian children throw stones against the Israeli occupation, the U.S. says they are terrorists. Whereas when Israel bombed the United Nations building in Lebanon while it was full of children and women, the U.S. stopped any plan to condemn Israel. At the same time that they condemn any Muslim who calls for his rights, they receive the top official of the Irish Republican Army at the White House as a political leader. Wherever we look, we find the U.S. as the leader of terrorism and crime in the world.”