Ferdinand I, Spanish king of Castile and León
or Ferdinand the Great, d. 1065, Spanish king of Castile (1035–65) and León (1037–65). He inherited Castile from his father, Sancho III of Navarre, conquered León, and took parts of Navarre from his brother García. Ferdinand fought successfully against the Moors and reduced to vassalage the Moorish kings of Zaragoza, Badajoz, Seville, and Toledo. At the Council of Coyanza (1050) he confirmed the laws of Alfonso V and introduced church reforms. He divided his kingdom among his sons: Castile went to Sancho II, León to Alfonso VI, and Galicia to García.
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Ferdinand I's Kingdom of Castile and León was divided between his three sons: Sancho II received Castile, Alfonso VI, León, and a new Kingdom of Galicia was broken off León for García. However, Sancho II prevented García from taking up his kingdom and then proceeded to attack Alfonso VI. In 1070, Sancho actually defeated Alfonso and drove him into exile, reassembling the whole kingdom of Ferdinand I. But when Sancho was killed in 1072, the whole kingdom immediately fell to Alfonso, who maintained its unity by imprisoning García until his death. How Sancho was killed is still a matter of uncertainty. He seems to have been meeting an incursion from Alfonso in exile, but the death may have been one of betrayal than just of battle. Whether Alfonso was even present is variously represented.
Source: http://www.friesian.com/perifran.htm#spain