The year is 732 A.D., and Europe is under assault. Islam, born a mere 110 years earlier, is already in its adolescence, and the Muslim Moors are on the march. Growing in leaps and bounds, the Caliphate, as the Islamic realm is known, has thus far subdued much of Christendom, conquering the old Christian lands of the Mideast and North Africa in short order. Syria and Iraq fell in 636; Palestine in 638; and Egypt, which was not even an Arab land, fell in 642. North Africa, also not Arab, was under Muslim control by 709. Then came the year...