The year is 632 A.D., and Muslim hordes have set their sights on the Mideast and North Africa -- the old Christian world. And the Caliphate, as the Islamic realm is called, will not be denied. Syria and Iraq fall in 636. Palestine is next in 638. And Byzantine Egypt and North Africa, not even Arab lands, are conquered by 642 and 709, respectively. Then, just two years later, the Muslims cross the Strait of Gibraltar and enter Iberia (now Spain and Portugal). The invasion of Europe has begun. And the new continent seems no impediment to Islam. After vanquishing...