In the ruins, police found twenty-two pounds of Goma-2 and two hundred copper detonators that were similar to those used in the train bombings. They also found the shredded remains of a videotape. These fragments were painstakingly reassembled, to the point where police could view the final statement of Fakhet and two other members of the cell, which called itself "the brigade situated in Al Andalus." Unless Spanish troops left Iraq within a week, the men had declared, "we will continue our jihad until martyrdom in the land of Tariq ibn Ziyad."

Al Andalus is the Arabic name for the portion of Spain that fell to Muslim armies after the invasion by the Berber general Tariq ibn Ziyad in 711. It includes not only the southern region of Andalusia, but most of the Iberian Peninsula. For the next eight hundred years, Al Andalus remained in Islamic hands. "You know of the Spanish crusade against Muslims, and that not much time has passed since the expulsion from Al Andalus and the tribunals of the Inquisition," Fakhet says on the tape. He is referring to 1492, when Ferdinand and Isabella completed the reconquest of Spain, forcing Jews and Muslims to convert to Catholicism or leave the Iberian Peninsula. "Blood for blood!" he shouts. "Destruction for destruction!"

Were these the true goals of Al Qaeda? Were the besieged terrorists in Leganes simply struggling to get Spain out of Iraq, or were they also battling to regain the lost colonies of Islam? In other words, were these terrorists who might respond to negotiation or appeasement, or were they soldiers in a religious fight to the finish that had merely been paused for five hundred years?

Less than a month after 9/11, Osama bin Laden and his chief lieutenant, Dr. Ayman al-Zawahiri, had appeared on Al Jazeera. "We will not accept that the tragedy of Al Andalus will be repeated in Palestine," Zawahiri said, drawing an analogy between the expulsion of the Moors from Iberia and the present-day plight of the Palestinians. The use of the archaic name Al Andalus left most Spaniards nonplussed. "We took it as a folkloric thing," Ramon Perez-Maura, an editor at ABC, told me. "We probably actually laughed." This January, bin Laden issued a "Message to the Muslim People," which was broadcast on Al Jazeera. He lamented the decline of the Islamic world: "It is enough to know that the economy of all Arab countries is weaker than the economy of one country that had once been part of our world when we used to truly adhere to Islam. That country is the lost Al Andalus."

The Muslims who were expelled from Al Andalus took refuge mainly in Morocco, Algeria, and Tunisia. Some families, it is said, still have the keys to their houses in Cordoba and Seville. But the legacy of Al Andalus persisted in Spain as well. Up until the Victorian era, the country was considered to be more a part of the Orient than of Europe. The language, the food, and the architecture were all deeply influenced by the Islamic experience-a rival past that Catholic Spain, in all its splendor, could never bury. "In modern Arabic literature, Al Andalus is seen as the lost paradise," Manuela Marin, a professor at the Consejo Superior de Investigaciones Cien-tificas, in Madrid, told me. "For Spain, the history of Al Andalus has a totally different meaning. After all, what we know as Spain was made in opposition to the Islamic presence on the peninsula. Only recently have people begun to accept that Islam was a part of Spain."

Although many Spanish historians have painted Moorish Spain as something other than paradise for Jews and Christians, for Muslims it remains not only a symbol of vanished greatness but a kind of alternative vision of Islam-one in which all the ills of present-day Islamic societies are reversed. Muslim tourists, including many heads of state, come to Spain to imagine a time when Islam was at the center of art and learning, not on the fringes. "The Alhambra is the number one Islamic monument," Malik A. Ruiz Callejas, the emir of the Islamic community in Spain and the president of Granada's new mosque, told me recently. "Back when in Paris and London people were being eaten alive by rats, in Cordoba everyone could read and write. The civilization of Al Andalus was probably the most just, most unified, and most tolerant in history, providing the greatest level of security and the highest standard of living."

Imams sometimes invoke the glory of Al Andalus in Friday prayers as a reminder of the price that Muslims paid for turning away from the true faith. When I asked Moneir el-Messery, of the M-30 mosque, if the Madrid bombers could have been motivated by the desire to recapture Al Andalus, he looked up sharply and said, "I can speak of the feeling of all Muslims. It was a part of history. We were here for eight centuries. You can't forget it, ever."

The fear that the "Moors" would one day return and reclaim their lost paradise-through either conquest or immigration-has created a certain paranoia in Spanish politics. Construction of the mosque in Granada was delayed for twenty-two years because of the intense anxiety surrounding the growing Islamic presence. In 1986, Spain joined the European Union; generous EU subsidies ignited an economic boom, drawing thousands of young men from North Africa. "The Muslims are young, and male, and they come by themselves," Mohammed el-Afifi, the director of press relations at the M-30 mosque, told me two years ago, when I visited him. "They don't speak Spanish, and they don't have much information about Spain. And they arrive with a different religion." At the time, Afifi placed the number of Arab immigrants in Spain at three hundred thousand. Now the number of Arabic-speaking immigrants is five hundred thousand, not including half a million illegals. The

Spanish government has encouraged official immigration from South America at the expense of North Africa, but smugglers in high-speed power boats make nightly drop-offs on the ragged Spanish coastline, and the frequent discovery of corpses washing up on the beaches testifies to the desperation of those who did not quite get to shore.

Muslim immigration is transforming all of Europe. Nearly twenty million people in the European Union identify themselves as Muslim. This population is disproportionately young, male, and unemployed. The societies these men have left are typically poor, religious, conservative, and dictatorial; the ones they enter are rich, secular, liberal, and free. For many, the exchange is invigorating, but for others Europe becomes a prison of alienation. A Muslim's experience of immigration can be explained in part by how he views his adopted homeland. Islamic thought broadly divides civilization into dar al-Islam, the land of the believers, and dar al-Kufr, the land of impiety.

France, for instance, is a secular country, largely Catholic, but it is now home to five million Muslims. Should it therefore be considered part of the Islamic world? This question is central to the debate about whether Muslims in Europe can integrate into their new communities or must stand apart from them. If France can be considered part of dar al-lslam, then Muslims can form alliances and participate in politics; they should have the right to institute Islamic law, and they can send their children to French schools. If it is a part of dar al-Kufr, then strict Muslims must not only keep their distance;

they must fight against their adopted country.

The Internet provides confused young Muslims in Europe with a virtual community. Those who cannot adapt to their new homes discover on the Internet a responsive and compassionate forum. "The Internet stands in for the idea of the ummah, the mytholo-gized Muslim community," Marc Sageman, the psychiatrist and former CIA officer, said. "The Internet makes this ideal community concrete, because one can interact with it." He compares this virtual ummah to romantic conceptions of nationhood, which inspire people not only to love their country but to die for it.