Forces of the Catholic Monarchs engage the combined Portuguese-Castilian armies of Afonso V and Prince John at the Battle of Toro.
The Battle of Toro was part of the War of the Castilian Succession, fought on 1 March 1476, near the city of Toro, between the Castilian-Aragonese troops of the Catholic Monarchs and the Portuguese-Castilian forces of Afonso V and Prince John of Portugal.
The battle was militarily inconclusive, as both sides claimed victory: the Castilian right wing was defeated by the forces under Prince John who possessed the battlefield, but the troops of Afonso V were beaten by the Castilian left-centre led by the Duke of Alba and Cardinal Mendoza.However, it was a major political victory for the Catholic Monarchs by assuring to Isabella the throne of Castile: The remnants of the nobles loyal to Juana de Trastmara adhered to Isabella. With great political vision, Isabella took advantage of the moment and summoned the 'Cortes' at Madrigal-Segovia (AprilOctober 1476). There her daughter was proclaimed sworn heiress of the Castile's crown, which was equivalent to legitimizing her own throne.
As noted by Spanish academic Antnio Serrano: "From all of this it can be deduced that the battle [of Toro] was inconclusive, but Isabella and Ferdinand made it fly with wings of victory. (...) Actually, since this battle transformed in victory; since 1 March 1476, Isabella and Ferdinand started to rule the Spanish throne. (...) The inconclusive wings of the battle became the secure and powerful wings of San Juan's eagle [the commemorative temple of the battle of Toro] ".The war continued until the peace of Alcovas (1479), and the official propaganda transformed the Battle of Toro into a victory which avenged Aljubarrota.
The Catholic Monarchs were Queen Isabella I of Castile and King Ferdinand II of Aragon, whose marriage and joint rule marked the de facto unification of Spain. They were both from the House of Trastámara and were second cousins, being both descended from John I of Castile; to remove the obstacle that this consanguinity would otherwise have posed to their marriage under canon law, they were given a papal dispensation by Sixtus IV. They married on October 19, 1469, in the city of Valladolid; Isabella was eighteen years old and Ferdinand a year younger. It is generally accepted by most scholars that the unification of Spain can essentially be traced back to the marriage of Ferdinand and Isabella.
Spain was formed as a dynastic union of two crowns rather than a unitary state, as Castile and Aragon remained separate kingdoms until the Nueva Planta decrees of 1707–1716. The court of Ferdinand and Isabella was constantly on the move, in order to bolster local support for the crown from local feudal lords. The title of "Catholic King and Queen" was officially bestowed on Ferdinand and Isabella by Pope Alexander VI in 1494, in recognition of their defence of the Catholic faith within their realms.