There are various theories on his family history, which remains uncertain; however, he was the grandfather of García Ramírez de Pamplona, King of Navarre, the first son of his daughter Cristina Rodríguez.

El Cid went on to lead the Castilian military campaigns against Sancho's brothers, Alfonso VI of León and García II of Galicia, as well as in the Muslim kingdoms in al-Andalus.

He became renowned for his military prowess in these campaigns, which helped expand the territory of the Crown of Castile at the expense of the Muslims and Sancho's brothers' kingdoms.

In 1086, an expeditionary army of North African Almoravids inflicted a severe defeat to Castile, compelling Alfonso to overcome the resentment he harboured against El Cid.

Over the next several years, however, El Cid set his sights on the kingdom-city of Valencia, operating more or less independently of Alfonso, while politically supporting the Banu Hud and other Muslim dynasties opposed to the Almoravids.

Although El Cid remained undefeated in Valencia, Diego Rodríguez, his only son and heir, died fighting against the Almoravids in the service of Alfonso in 1097.

After El Cid's death in 1099, his wife, Jimena Díaz, succeeded him as ruler of Valencia, but she was eventually forced to surrender the principality to the Almoravids in 1102.

[citation needed] El Cid was born Rodrigo Díaz circa 1043 in Vivar,[16] also known as Castillona de Bivar, a small town about ten kilometers (or six miles) north of Burgos, the capital of Castile.

[citation needed] As a young man in 1057, El Cid fought against the Moorish stronghold of Zaragoza, making its emir al-Muqtadir a vassal of Sancho.

One legend has said that during the conflict, El Cid killed an Aragonese knight in single combat, thereby receiving the honorific title "Campeador".

[17] When Ferdinand died, Sancho continued to enlarge his territory, conquering both Christian strongholds and the Moorish cities of Zamora and Badajoz.

[18] Since Sancho died unmarried and childless, all of his power passed to his brother Alfonso who, almost immediately, returned from exile in Toledo and took his seat as king of Castile and León.

According to the 11th century epic poem Cantar de mio Cid, the Castilian nobility led by El Cid and a dozen "oath-helpers" forced Alfonso to swear publicly on holy relics multiple times in front of Santa Gadea (Saint Agatha) Church in Burgos that he did not participate in the plot to kill his brother.

In 1081, El Cid went on to offer his services to the king of Zaragoza, Yusuf al-Mu'taman ibn Hud, and served both him and his successor, al-Musta'in II.

He was given the title El Cid (The Master) and served as a leading figure in a diverse Moorish force consisting of Muwallads, Berbers, Arabs, and Malians within the respective Taifa.

[citation needed] According to Moorish accounts: Andalusi Knights found El Cid their foe ill, thirsty and exiled from the court of Alfonso, he was presented before the elderly Yusuf al-Mu'taman ibn Hud and accepted command of the forces of the Taifa of Zaragoza as their Master.In his History of Medieval Spain (Cornell University Press, 1975), Joseph F. O'Callaghan writes: That kingdom was divided between al-Mutamin (1081–1085) who ruled Zaragoza proper, and his brother al-Mundhir, who ruled Lérida and Tortosa.

The Almoravids, a Berber dynasty from North Africa, led by Yusuf ibn Tashfin, were asked to help defend the divided Moors from Alfonso.

[citation needed] Terrified after his crushing defeat, Alfonso recalled El Cid, rewarding him lavishly with lands and lordships, such as the fortress of Gormaz.

In May 1090, El Cid defeated and captured Berenguer in the Battle of Tébar (nowadays Pinar de Tévar, near Monroyo, Teruel).

[citation needed] El Cid gradually came to have more influence in Valencia, then ruled by Yahya al-Qadir, of the Hawwara Berber Dhulnunid dynasty.

Originally buried in Castile in the monastery of San Pedro de Cardeña, his body now lies at the center of Burgos Cathedral.

[28] After his demise, but still during the siege of Valencia, legend holds that Jimena ordered that the corpse of El Cid be fitted with his armor and set on his horse, Babieca, to bolster the morale of his troops.

In several variations of the story, the dead Rodrigo and his knights win a thundering charge against Valencia's besiegers, resulting in a war-is-lost-but-battle-is-won catharsis for generations of Christian Spaniards to follow.

[29] During his campaigns, El Cid often ordered that books by classic Roman and Greek authors on military themes be read aloud to him and his troops, for both entertainment and inspiration before battle.

El Cid's army had a novel approach to planning strategy as well, holding what might be called "brainstorming" sessions before each battle to discuss tactics.

Another legend states that in a competition of battle to become King Sancho's "Campeador", or champion, a knight on horseback wished to challenge El Cid.

This version says Babieca was raised in the royal stables of Seville and was a highly trained and loyal war horse, not a foolish stallion.

[31] A weapon traditionally identified as El Cid's sword, Tizona, used to be displayed in the Army Museum (Museo del Ejército) in Toledo.

This poem, along with similar later works such as the Mocedades de Rodrigo, contributed to portray El Cid as a chivalric hero of the Reconquista,[38] making him a legendary figure in Spain.

Claude Debussy began work in 1890 on an opera, Rodrigue et Chimène, which he abandoned as unsuitable for his temperament; it was orchestrated for performance by Edison Denisov circa 1993.