Nearly thirteen hundred years ago today, on May 28, 722[i], a little known but profoundly important battle was waged that set the tone for the next eight hundred years of Christian-Muslim "coexistence" in Spain: the Battle of Covadonga. Ten years earlier, Arabs and Africans, both under the banner of Islam, had "godlessly invaded Spain to destroy it," to quote from the Chronicle of 754. Once on European soil, they "ruined beautiful cities, burning them with fire; condemned lords and powerful men to the cross; and butchered youths and infants with the sword." After meeting and beating Spain's Visigothic nobles at...