Architect of New War on the West

He arrived in Spain in 1985. He married a Spanish woman who had converted to Islam, and through that connection, he became a dual Spanish-Syrian citizen. He also made contacts with other Syrian emigres who belonged to the Muslim Brotherhood. His neighbor in a small town in the province of Granada was Tayssir Alouni, a journalist for the al-Jazeera satellite television network who would later interview Osama bin Laden. Another friend was Imad Eddin Barakat Yarkas, who was convicted last fall on charges of running an al-Qaeda cell in Spain.

In 1987, Nasar journeyed to Pakistan and Afghanistan to help Muslim fighters in their rebellion against Soviet forces in Afghanistan. He trained at camps, met bin Laden and joined the ruling council of al-Qaeda, according to a Spanish indictment filed against him.

When he returned to Spain in 1992, he concentrated on building his own cell there and also traveled widely in Europe to set up other al-Qaeda groups in Italy and France, according to the Spanish.

"He's pretty much designed the structure of the cells that have operated in Europe," said Rogelio Alonso, a terrorism expert and professor at King Juan Carlos University in Madrid. "He was the one with the prominent role as the individual who had the links with the higher echelons of al-Qaeda."

Although Nasar attracted the notice of Spanish police, investigators did not classify him as a serious threat. According to Spanish court papers, detectives had Nasar under surveillance in 1995. But when he moved to London that year, they stopped paying attention.

In London, Nasar led an above-ground life as a writer and voice of Islamic extremism. He did publicity work for al-Qaeda, helping to arrange interviews with bin Laden in Afghanistan for CNN and the BBC.

He edited an Arabic-language newsletter called al-Ansar, which was devoted primarily to the cause of fundamentalists fighting a long and bloody civil war in Algeria. Even in London's sizable community of Arab exiles and radical Muslims, Nasar stood out for his strong views and unwillingness to compromise.

In his newsletter, he defended the Armed Islamic Group, the Algerian rebel force known by its French acronym, GIA, for targeting Algerian civilians in a series of massacres that destroyed entire villages. When other Arab dissidents decried the tactics, Nasar turned on them as well, denouncing his critics in letters and in person.

"In Algeria, he pushed people to violence," said one Arab exile living in Britain who tangled with Nasar in the mid-1990s. "He was not just an editor. He served as a strategist for those people and played a very bad role in what happened in Algeria," said the exile, who spoke on condition of anonymity, saying he feared harassment from al-Qaeda supporters.

British intelligence officials also took note of Nasar's activities in their country and questioned him on at least two occasions, according to people who knew him. But he was never placed under formal investigation, they said.

"He's very intelligent and powerful in making his arguments," said an Arab dissident who knew Nasar well and also spoke on condition of anonymity. "But he is also a very difficult man. His tough attitude created many, many enemies for him, even in jihadi circles."

With his pale white skin and red hair, Nasar physically blended into British society more easily than many Islamic fundamentalists. But he sometimes struggled to reconcile his beliefs with his surroundings.