To listen to Europe’s far right, it would be easy to conclude that the continent is poised for another round of bitter conflict with a centuries-old adversary. “The first Islamic invasion of Europe was stopped at [the battle of] Poitiers in 732. The second was halted at the gates of Vienna in 1683. Now we have to stop the current stealth invasion,” argues Geert Wilders, the leader of the Dutch Party for Freedom, which claims that Islamic doctrine encourages terrorism. It’s rabble-rousing stuff. But underlying Wilders’s polemic is an argument shared by many more mainstream right-leaning thinkers on both sides of the Atlantic. Europe, its will sapped by secularism and anything-goes tolerance, has allowed decades of mass immigration without serious challenge. Too feeble to defend their own values, governments have been ready to appease Muslim opinion and must expect the worst. The argument has been gaining ground for some time—fed by alarmist and highly speculative projections from writers like the Canadian Mark Steyn, author of the bestselling America Alone—that immigration and high birthrates could mean that Muslims will make up 40 percent of Europe’s population by 2025. Similar and very public warnings have come from American diplomat Timothy Savage, who claimed that forecasts of a Muslim majority in Western Europe by midcentury “may not be far off the mark” if present trends continue, which would heighten the risk of conflict. The British historian Niall Ferguson has written that “a youthful Muslim society to the south and east of the Mediterranean is poised to colonize—the term is not too strong—a sene-scent Europe.” And the American journalist Christopher Caldwell forecasts that an “anchored” and “confident” Islam looks likely to impose its will on an “insecure” and “relativistic” European culture. The gloomiest commentators, including Steyn and the conservative Ameri-can writer Tony Blankley, talk of an emerging “Eurabia” hostile to American interests and in thrall to Islam. These warnings chime with public fears that Europe has already become an incubator for worldwide terrorism. After all, the September 11 hijackers plotted in Germany, and homegrown terrorists were involved in the Madrid and London attacks. Concern is growing that a swelling immigrant population resistant to assimilation or integration will steal jobs and strain public services. Last year a Pew poll found that about half of respondents in Spain and Germany held negative views of Muslims. In Spain the figure had climbed 15 points, to 52 percent, since 2004. In the June elections to the European Parliament, Wilders’s party won 17 percent of the national vote in the Netherlands. The anti-immigrant British National Party, which warned of the “creeping Islamification” of British society, won its first two seats. In Austria the right-wing Freedom Party almost doubled its share of the vote, at 13 percent. William Underhill reports.