For almost seven hundred years, Spain was the battleground for the opposing forces of the Islamic Caliphate and Western Christian forces. Both Muslims and Christian were motivated by religious conviction, which inspired the warfare. The initial Islamic invasion of Iberia was sudden and unexpected. The varied Moorish tribes of Morocco united under the leadership of Arab generals sent by the reigning Umayyad caliph and crossed the Straits of Gibraltar in 711 under the leadership of the Berber Tariq ibn Ziyad. Tariq won a swift victory at the Guadalete and defeated and killed the reigning Gothic king, Roderic.[5] In a campaign lasting eight years, the whole of Iberia was subjected to Umayyad authority, except for the Asturias mountain range in the far northwest and the pockets of resistance in Navarre. The Islamic offensive ultimately paused after the losses it suffered in Frankland and in the Asturias, where battles such as those at Tours and Covadonga showed some of the potential weaknesses of the Arab methods of warfare.[6]
The Islamic conquest was only very slowly undone, over the course of seven centuries in what the Christians of Spain called the Reconquista. Three main forces were involved in this process, the Visigothic holdouts in the Asturias, the holdouts in Navarre and the Pyrenees, and the Franks of Aquitaine. The Reconquista, as a concerted effort to remove the Muslims from the territories they held, commenced in the reign of Alfonso I (739 – 757). Alfonso led an offensive into the valley of the Duero and left the region depopulated, the so-called "Desert of the Duero". For the next century, this prevented any serious Islamic incursions into the Christian territories of the north. During the late eighth and early 9th centuries, the Franks under their Carolingian rulers took up the cause of reconquest along the Mediterranean littoral. By 797, Charlemagne's son, Louis the Pious, captured Barcelona, establishing a clear bulwark against future invasions. The Basques extended their kingdom as far as Nájera, and a widespread repoblación of the depopulated areas began, extending Christian borders southwards.[7]
Despite a resurgence during the 10th century, the Caliphate of Córdoba's attempts to reverse the Reconquista failed, and by the 11th century, Christian Iberia was united under Sancho the Great, the King of Navarre, whilst the caliphate was divided and engulfed by civil war, the period of the taifas. The 11th century saw the development of a concept of Christian holy war, to be waged against Islam with the purpose of the Christians recapturing long lost territories - the Crusade. Crusading, under other names, also took place in Spain; Franks and Normans and even Papal troops took to Spain in increasing numbers to join the locals in their fight against "the Moor." The last threat of the 11th century came in the form of the Almoravids, who with their well disciplined forces first established a hegemony over Morocco and then extended it over al-Andalus. While the Reconquista paused in the west, to the east Alfonso the Battler, the King of Aragon, redoubled efforts to retake the valley of the Ebro. In 1212, the Reconquistadores gained a decisive victory over the Almohads at the Battle of Las Navas de Tolosa. Shortly after the battle, the Castilians took Baeza and, then, Úbeda, major fortified cities near the battlefield, and gateways to invade Andalucia. Thereafter, Ferdinand III of Castile retook Córdoba in 1236, Jaén in 1246, and Seville in 1248; then he took Arcos, Medina-Sidonia, Jerez and Cádiz, effectively bringing the bulk of the reconquista to a conclusion.
http://en.wikipedia.org/wiki/Military_history_of_Spain#Islamic_conquest_and_Reconquista
The Ghost of General Lee ... http://www.youtube.com/watch?v=ooz3eqWRdlc&feature=related