9th to 11th centuries: The beginnings
According to the chronicles of Alfonso III of Asturias; the first reference to the name "Castile" (Castilla) can be found in a document written during AD 800. In Al-Andalus chronicles from the Cordoban Caliphate, the oldest sources refer to it as Al-Qila, or "the castled" high plains past the territory of Alava, more south to it and the first encountered in their expeditions from Zaragoza. The name reflects its origin as a march on the eastern frontier of the Kingdom of Asturias, protected by castles, towers or castra.
The County of Castile, bordered in the south by the northern reaches of the Spanish Sistema Central mountain system, just north of modern-day Madrid province. It was re-populated by inhabitants of Cantabria, Asturias, Vasconia and Visigothic and Mozarab origins. It had its own Romance dialect and customary laws.
From the first half of the 9th century until the middle of the century, in which it came to be paid more closer attention to, its administration and defense by the monarchs of Leon – due the increased incursions from the Emirate of Córdoba – its first repopulation settlements were led by small abbots and local counts from the other side of the Cantabrian ridge neighbor valleys, Trasmiera and
Primorias and smaller ones, being its first settlers from the contiguous maritime valleys of Mena and Encartaciones in nearby Biscay, some of whom had abandoned those exposed areas of the Meseta a few decades earlier, and taken refuge by the much dense and intractable woods of the Atlantic valleys, so they were not that foreign to them.
A mix of settlers from the Cantabrian and Basque coastal areas, which were recently swelled with refugees, was led under the protection of Abbot Vitulus and his brother, count Herwig, as registered in the local charters they signed around the first years of the 800's. The areas that they settled didn't extend far from the Cantabrian southeastern ridges, and not beyond the southern reaches of the high Ebro river valleys and canyon gores.
The first Count of a wider and more united Castile was Rodrigo in 850, under Ordoño I of Asturias and Alfonso III of Asturias, who settled and fortified the ancient Cantabrian hill town of Amaya, much farther west and south of the Ebro river to offer a more easy defense and command of the still functional Roman Empire main highway passing by, south of the Cantabrian ridge all the way to Leon, from the Muslim military expeditions. Subsequently, the region was subdivided, separate counts being named to Alava, Burgos, Cerezo & Lantarón, and a reduced Castile. In 931 the County was reunified by Count Fernán González, who rose in rebellion against the Kingdom of León, successor state to Asturias, and achieved an autonomous status, allowing the county to be inherited by his family instead of being subject to appointment by the Leonese king.
11th and 12th Centuries: Expansion and Union with the Kingdom of León
Kingdom of Castile (Castilla) in 1037
The minority of Count García Sánchez led Castile to accept Sancho III of Navarre, married to the sister of Count García, as feudal overlord. García was assassinated in 1028 while in León to marry the princess Sancha, sister of Bermudo III of León. Sancho III, acting as feudal overlord, appointed his younger son (García's nephew) Ferdinand as Count of Castile, marrying him to his uncle's intended bride, Sancha of León. Following Sancho's death in 1035, Castile returned to the nominal control of León, but Ferdinand, allying himself with his brother García Sánchez III of Navarre, began a war with his brother-in-law Vermudo. At the Battle of Tamarón Vermudo was killed, leaving no surviving heirs. In right of his wife, Ferdinand then assumed the royal title as king of León and Castile, for the first time associating the royal title with the rule of Castile.
When Ferdinand I died in 1065, the territories were divided among his children. Sancho II became King of Castile, Alfonso VI, King of León and García, King of Galicia, while his daughters were given towns, Urraca, Zamora, and Elvira, Toro.
Sancho II allied himself with Alfonso VI of León and together they conquered, then divided Galicia. Sancho later attacked Alfonso VI and invaded León with the help of El Cid, and drove his brother into exile, thereby reuniting the three kingdoms. Urraca permitted the greater part of the Leonese army to take refuge in the town of Zamora. Sancho laid siege to the town, but the Castilian king was assassinated in 1072 by Bellido Dolfos, a Galician nobleman. The Castilian troops then withdrew.
As a result, Alfonso VI recovered all his original territory of León, and became the king of Castile and Galicia. This was the second union of León and Castile, although the two kingdoms remained distinct entities joined only in a personal union. The [oath taken by El Cid] before Alfonso VI in Santa Gadea de Burgos regarding the innocence of Alfonso in the matter of the murder of his brother is well known.
During the first years of the 12th century, Sancho, the only son of Alfonso VI, died, leaving only his daughter. Due to this, Alfonso VI took a different approach from other European kingdoms, including France. He gave his daughters, Elvira, Urraca, and Theresa in marriage to Raymond of Toulouse, Raymond of Burgundy, and Henry of Burgundy respectively. In the Council of Burgos in 1080 the traditional Mozarabic rite was replaced by the Roman one.
Upon his death, Alfonso VI was succeeded by his daughter, the widowed Urraca, who then married Alfonso I of Aragon, but they almost immediately fell out. Alfonso tried unsuccessfully to conquer Urraca's lands, before he repudiated her in 1114. Urraca also had to contend with attempts by her son from her first marriage, the king of Galicia, to assert his rights. When Urraca died, this son became king of León and Castile as Alfonso VII. During his reign, Alfonso VII managed to annex parts of the weaker kingdoms of Navarre and Aragón which fought to secede after the death of Alfonso I of Aragon.
Alfonso VII refused his right to conquer the Mediterranean coast for the new union of Aragón with the County of Barcelona (Petronila and Ramón Berenguer IV).
12th Century: A Link Between Christianity and Islam
The centuries of Moorish rule had established Castile's high central plateau as a vast sheep pasturage; the fact that the greater part of Spanish sheep-rearing terminology was derived from Arabic underscores the debt.
The 8th and 9th centuries was preceded by a period of Umayyad conquests, as Arabs took control of previously Hellenized areas such as Egypt and Syria in the 7th century. It was at this point they first encountered Greek ideas, though from the beginning, many Arabs were hostile to classical learning. Because of this hostility, the religious Caliphs could not support scientific translations. Translators had to seek out wealthy business patrons rather than religious ones. Until Abassid rule in the 8th century, however, there was little work in translation. Most knowledge of Greek during Umayyad rule was gained from scholars of Greek who remained from the Byzantine period, rather than through widespread translation and dissemination of texts. A few scholars argue that translation was more widespread than is thought during this period, but this remains the minority view.
The main period of translation was during Abbasid rule. The 2nd Abassid Caliph Al-Mansur moved the capital from Damascus to Baghdad. Here he founded a great library, containing Greek Classical texts. Al-Mansur ordered this collection of world literature translated into Arabic. Under al-Mansur, and by his orders, translations were made from Greek, Syriac, and Persian. The Syriac and Persian books themselves were translations from Greek or Sanskrit.
Territories of Castile, Christians and Muslims during 12th Century
A legacy of the 6th century King of Persia, Anushirvan (Chosroes I) the Just was the introduction of many Greek ideas into his kingdom. Aided by this knowledge and the juxtaposition of beliefs, the Abassids considered it valuable to look at Islam with Greek eyes, and to look at the Greeks with Islamic eyes. Abassid philosophers also advanced the idea that Islam had, from the very beginning, stressed the gathering of knowledge as a key part of the religion. These new ideas enabled the amassing and translation of Greek concepts to disseminate like never before.
During the 12th century, Europe enjoyed great advances in intellectual achievements, sparked in part by the kingdom of Castile's conquest of the great cultural center of Toledo (1085). There Arabic classics were discovered, and contacts established with the knowledge and works of Muslim scientists. In the first half of the century a translation program, called the "School of Toledo", translated many philosophical and scientific works from the Classical Greek and the Islamic worlds into Latin. Many European scholars, including Daniel of Morley and Gerard of Cremona travelled to Toledo to gain further knowledge.
The Way of St. James further enhanced the cultural exchange between the kingdoms of Castile and León and the rest of Europe.
The 12th century saw the establishment of many new religious orders, like the rest of Europe, such as Calatrava, Alcántara and Santiago; and the foundation of many Cistercian abbeys.