By Raymond Ibrahim, The Stream - On July 16, 1212, atop the windswept plains of Las Navas de Tolosa, Christendom and Islam clashed in one of the most consequential battles of the Middle Ages — an event that shattered an empire, galvanized a continent, and echoes still in the political currents of modern Spain and among Islamist terrorists who vow vengeance for it... It had been 500 years since the armies of Muhammad first crossed the Strait of Gibraltar and began their conquest of Iberia in 711. In their wake, most of the peninsula fell under the crescent.