In 1074, Alfonso VI's vassal and friend Al-Mamun, king of the Taifa of Toledo died of poisoning in Córdoba, and was succeeded by his grandson Al-Qádir, who asked for help from the Leonese monarch to end an uprising against him. Alfonso VI took advantage of this request to besiege Toledo, which finally fell on 25 May 1085. After losing his throne, Al-Qádir was sent by Alfonso VI as king of the Taifa of Valencia under the protection of Álvar Fáñez. To facilitate this operation and to recover payment of the parias owed by the city, which had failed to pay him since the previous year, Alfonso VI besieged Zaragoza in the spring of 1086. In early March, Valencia accepted the rule of Al-Qádir.

The occupation of Toledo led to the taking of cities such as Talavera and fortresses including the castle of Aledo. He also occupied Mayrit (now Madrid) in 1085 without resistance, probably by capitulation. The incorporation of the territory situated between the Sistema Central and the Tajo river would serve as the base of operations for the Kingdom of León, from where he could launch more attacks against the Taifas of Cordoba, Seville, Badajoz and Granada.