They came in the early eighth century across the Straits of Gibraltar, unleashing terror and carnage across Iberia “like a desolating storm.” They were stopped deep inside today’s France, at Tours, by Charles Martel in 732. They kept attacking Europe throughout the Middle Ages, but their next sustained assault was at her vulnerable southeastern flank, taking advantage of Byzantium’s weakened state after the infamous Fourth Crusade. They conquered Constantinople and destroyed the Christian nations of Bulgaria, Serbia, Hungary. They were finally stopped at the gates of Vienna in 1683.

Europe seemed safe over the ensuing 250 years of unprecedented demographic, scientific, technological, and geopolitical advance. The “sick man on the Bosphorus” was reduced to a mere object of European imperial ambitions, while “Arabia,” irrelevant to the civilized world, remained stuck in its primitive ways.

Then Europe attempted suicide with the Great War, sealed with its sequel in 1939-45. Her subsequent material recovery was a mirage. Dechristianized and focused on the need for cheap labor regardless of its source, she imported millions of Muslim immigrants in the 1960’s and 70’s—Turks to Germany, Pakistanis to Britain, Algerians to France, and a mix of them all to Benelux, Scandinavia, Austria. A generation later a multimillion...