Among the factors leading to the French and Dutch rejections of the European constitution last week, none looms more ominously than the nightmare of antagonism between ''the West" and Islam. Many Europeans fear a rising tide of green, both within the continent and from outside it. Where once communists threatened, now Muslims do. A new wall is being built.

Muslims, meanwhile, see a flood of contempt in pressures on immigrant communities in European cities, in restrictions on Islamic expression, and in openly expressed reservations about Turkey's admission to the EU precisely because of its Islamic character. Given escalations of the war in Iraq together with widely reported instances of Koran-denigration by US interrogators, such trends in Europe make the global war on terror seem expressly a war against Islam. The ''clash of civilizations" seems closer at hand than ever.

To make sense of this dangerous condition, it can help to recall some of the forgotten or misremembered history that prepared for it, from the remote origins of the conflict to its manifestations in the not so distant past. As the story is usually told in Europe and America, the problem began when a jihad-driven army of ''infidel" Saracens, having brutalized Christians in the ''Holy Land," threatened ''Christendom" itself with conquests right into the heart of present-day France. Charles Martel is the hero of primal European romances because he defeated the Muslim army near Tours in 733. But for Martel, Edward Gibbon wrote, ''the Koran would now be taught in the schools of Oxford."

Across subsequent centuries, in the European memory, Islam posed the great threat to the emerging Christian order. But was that so? Lombards, Normans, Vikings, forces from the Slavic east, and violent contests among Christians themselves all wreaked havoc in Europe, even in Martel's time. As I learned from the historian Tomaz Mastnak, the threat from the Saracens was one among many. It was defined as transcendent only with the later Crusades, when Latin Christian armies set out to rescue that ''Holy Land" and roll back Islamic conquests. The crusading impulse presumed a demonizing of Saracens that was justified neither by the threat they actually posed nor by their treatment of Christians in Palestine. Indeed, chronicles of the earlier period take little or no notice of the religion of Saracens. Religious co-existence, famous in Iberia, was a mark of other lands conquered by Arabs. Europe's initiating ''holy war" with Islam, that is, was based on flawed intelligence, propaganda, and threat exaggeration.

The poison flower of the Crusades, with their denigrations of distant cultures, was colonialism. The dark result of European imperial adventuring in the Muslim world was twofold: first, the usual exploitation of native peoples and resources, with attendant destruction of culture, and, second, the powerful reaction among Muslims and Arab populations against colonialism, a reaction that included an internal corrupting of Islamic traditions. The accidental wealth of oil in the Middle East made both external exploitation and internal corruption absolutely ruinous. The political fanaticism that has lately seized the Arab Islamic religious imagination (exemplified in Osama bin Laden) is rooted more in a defensive fending off of assault from ''the West" than in anything intrinsic to Islam. The American war on terror, striking the worst notes of the old imperial insult, only exacerbates this reactionary fanaticism (generating, for example, legions of suicide bombers).

Having forgotten the deeper history, nervous Europeans seem also to have forgotten how large numbers of Muslims settled in the continent's cities in the first place. In the 1960s and 1970s, Turks, Arabs, and North Africans were welcomed as ''guest workers," taking up menial labor with the implicit understanding that they could never hope to be received as citizens of the nations that exploited them. The rank injustice of a system depending on a permanent underclass was bound to issue in political resistance, and now it has, but with a religious edge.

The point is that this conflict has its origins more in ''the West" than in the House of Islam. The image of Muslims as prone to violence by virtue of their religion was mainly constructed across centuries by Europeans seeking to bolster their own purposes, a habit of politicized paranoia that is masterfully continued by freaked-out leaders of post-9/11 America. They, too, like prelates, crusaders, conquistadors, and colonizers, have turned fear of Islam into a source of power. This history teaches that such self-serving projection can indeed result in the creation of an enemy ready and willing to make the nightmare real.

James Carroll's column appears regularly in the Boston Globe.