Back in the 1930s, when white men were preparing for another round of mutual slaughter, few of them paid any attention to the Muslim world. They assumed it to be a backward region that history had long since passed by. One man saw it differently. The great Catholic polemicist Hilaire Belloc, an Englishman of French ancestry, remembered Islam's past and predicted, in his book THE GREAT HERESIES, that it would one day challenge the West again. As late as 1683 its armies had threatened to conquer Europe, penetrating all the way to Vienna; Belloc believed that a great Islamic revival,...