In the 8th century, Muslims invaded the Spanish peninsula from North Africa and conquered it almost entirely. Only a northern part and the border with France could be held by the Christians and thus the further Muslim conquest of Europe be prevented.
The reconquest of the Spanish peninsula, also called Reconquista, took place in several stages. From the 10th century, the caliphate created by the Muslims first fell apart. 910 was the west of the Kingdom of Galicia and Leon, which united in the 11th century with the newly created Castile. After the invasion of the Franks from the north emerged on the eastern part of the peninsula, the kingdoms of Navarre, Aragón and Catalonia. Although there were conflicts and conflicts among the small states as well, almost the entire north of Spain was at least once again in Christian hands.
At that time, conflicts between Christians and Muslims, but also between the Christian minorities and even among the Muslims themselves dominated everyday life. The actual reconquest of the peninsula by the Muslims did not take effect until the end of the 11th century. So Ferdinand I of León expanded in 1074 his power area in a southerly direction and conquered Coimbra. In 1077, the king of Castile called Alfonso VI. himself Emperor of the entire Spanish territory and led his army also to the south where he captured Toledo in 1085 and the Muslim rulers of Al-Andalus in panic. These went into 1086 in a counter-offensive and beat Alfonso's army in 1086 at Sagrajas. They had to realize, however, that the real war had just begun.
In 1094, after a 20-month siege, El Cid, the commander of Alfonso, succeeded in taking the city of Valencia and establishing himself as ruler in the name of Alfonso. These ongoing conflicts led to the war against the Muslim Moors being proclaimed a holy struggle to preserve the Christian faith in 1095.
So it came that Alfonso I of Aragón and Navarre was able to conquer more territories until 1118, including the city of Zaragoza which lies to the west of Barcelona. In 1139 Afonso Henrique's Earl of Portucale, later King Afonso I of Portugal, succeeded in making a decisive victory over the Muslims at Ourique (south of modern-day Portugal). Out of this victory came the country of Portugal.
In the middle of the 12th century, heavily-weakened Muslims received support from their conquered territories in North Africa. So many Almohads came to the south of Spain to renew Islam on the peninsula and to recapture the lost areas. With a campaign at the end of the 12th century succeeded in the Muslims in the Battle of Alacros 1195 Alfonso VIII inflict a crushing defeat and draw the luck of war again on their side. It was followed by further victories until in 1212 at the Battle of Las Navas de Tolosa by tactical skill the almost 300,000-strong army of Muslims was almost completely destroyed by Alfonso's army. By this defeat it was no longer possible for the Muslims to establish a military resistance against the Christian armies and lost gradually more and more areas until in the last battle 1492 in Granada also the last Muslims from the peninsula were expelled.
By the marriage 1469 of the Catholic kings Ferdinand and Isabella, the kingdoms of Navarre, Aragón and Castile united to the present state of Spain. After the last Muslims were expelled from the peninsula in 1492, a time of Inquisition started, destroying any traces of Muslims.
You can find the right literature here:
Reconquest and Crusade in Medieval Spain
Drawing from both Christian and Islamic sources, Reconquest and Crusade in Medieval Spain demonstrates that the clash of arms between Christians and Muslims in the Iberian peninsula that began in the early eighth century was transformed into a crusade by the papacy during the twelfth and thirteenth centuries. Successive popes accorded to Christian warriors willing to participate in the peninsular wars against Islam the same crusading benefits offered to those going to the Holy Land. Joseph F. O'Callaghan clearly demonstrates that any study of the history of the crusades must take a broader view of the Mediterranean to include medieval Spain.
Following a chronological overview of crusading in the Iberian peninsula from the late eleventh to the middle of the thirteenth century, O'Callaghan proceeds to the study of warfare, military finance, and the liturgy of reconquest and crusading. He concludes his book with a consideration of the later stages of reconquest and crusade up to and including the fall of Granada in 1492, while noting that the spiritual benefits of crusading bulls were still offered to the Spanish until the Second Vatican Council of 1963.
Although the conflict described in this book occurred more than eight hundred years ago, recent events remind the world that the intensity of belief, rhetoric, and action that gave birth to crusade, holy war, and jihad remains a powerful force in the twenty-first century.
Kingdoms of Faith: A New History of Islamic Spain
In Kingdoms of Faith, award-winning historian Brian A. Catlos rewrites the history of Islamic Spain from the ground up, evoking the cultural splendor of al-Andalus, while offering an authoritative new interpretation of the forces that shaped it.
Prior accounts have portrayed Islamic Spain as a paradise of enlightened tolerance or the site where civilizations clashed. Catlos taps a wide array of primary sources to paint a more complex portrait, showing how Muslims, Christians, and Jews together built a sophisticated civilization that transformed the Western world, even as they waged relentless war against each other and their coreligionists. Religion was often the language of conflict, but seldom its cause--a lesson we would do well to learn in our own time.
El Cid and the Reconquista 1050-1492
The very name El Cid sums up much of the special character of medieval Spanish warfare. It comes from the Arabic al sayyid, master or chieftain, and seems to have been given to Rodrigo de Vivar by his Muslim foes. But was it given in recognition of El Cid's victories against Islam in the 'Reconquista' – or because this Castilian nobleman was as content to serve beside the Muslims as to fight them? The story of the Christian conquest of the Iberian peninsula which gave rise to the legend of El Cid, is here examined by David Nicolle, who outlines the history, tactics, arms and armour of the period.
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