The Kingdom of Castile was a polity in the Iberian Peninsula during the Middle Ages. It traces its origins to the 9th-century County of Castile, as an eastern frontier lordship of the Kingdom of León. During the 10th century, the Castilian counts increased their autonomy, but it was not until 1065 that it was separated from the Kingdom of León and became a kingdom in its own right. Between 1072 and 1157, it was again united with León, and after 1230, the union became permanent.
Throughout that period, the Castilian kings made extensive conquests in southern Iberia at the expense of the Islamic principalities. The Kingdoms of Castile and of León, with their southern acquisitions, came to be known collectively as the Crown of Castile, a term that also came to encompass overseas expansion.
9th to 11th centuries: 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 the 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, further south than 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, in a territory formerly called Bardulia.
The County of Castile, bordered in the south by the northern reaches of the Spanish Sistema Central mountain system, was 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 attention, it was administered and defended by the monarchs of Leon, due to 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, from the contiguous maritime valleys of Mena and Encartaciones in nearby Biscay; some of those settlers had abandoned those exposed areas of the Meseta a few decades earlier, and taken refuge in the much denser and more 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 800s. The areas that they settled did not 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. He settled and fortified the ancient Cantabrian hill town of Amaya, west and south of the Ebro river, which offered an easier defense from the Muslim military expeditions and command of the main highway, still functional from the Roman Empire, passing by, south of the Cantabrian ridge all the way to Leon. 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
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 was given Zamora, and Elvira was given 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.
During the first years of the 12th century, Sancho, the only son of Alfonso VI, died, leaving only his daughter. Because of 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.