Despite a few initial successes by the supporters of Joanna, a lack of military aggressiveness by Afonso V and the stalemate[1] in the Battle of Toro (1476) led to the disintegration of Joanna's alliance and the recognition of Isabella in the Courts of Madrigal-Segovia (April–October 1476): "In 1476, immediately after the indecisive battle of Peleagonzalo [near Toro], Ferdinand and Isabella hailed the result as a great victory and called Courts at Madrigal.

[3][4][5] The war concluded in 1479 with the Treaty of Alcáçovas, which recognized Isabella and Ferdinand as sovereigns of Castile and granted Portugal hegemony in the Atlantic, with the exception of the Canary Islands.

[citation needed] In 1465, a group of nobility called the Liga Nobiliaria assembled in Ávila and overthrew King Henry, replacing him with Alfonso.

[citation needed] Henry IV regained the throne, but the title of heir became disputed between Joanna, his daughter, and Isabella, his half-sister.

[citation needed] The Kingdom of France and the Crown of Aragon maintained a long-held rivalry for the control of Roussillon and, more recently, for hegemony in Italy.

On the possibility that the heir to the throne of Aragon would also become King of Castile, Louis XI of France officially positioned himself on the side of Joanna and Afonso in September 1475.

[citation needed] During the first half of the century, Castile staged the conquest of a few of the Canary Islands (Lanzarote, Fuerteventura, Hierro, and La Gomera) by feudal pacts, first with Norman knights and later with Castilian nobles.

[citation needed] Beginning in 1452, Pope Nicholas V and his successor, Callixtus III, modified the previous policy of the neutrality of the Holy See and issued a series of bulls favourable to Portugal.

The King of Portugal adopted a freer commercial policy that allowed foreign subjects to trade on the African coasts, in exchange for taxes.

[citation needed] In August 1475, after the start of the war, Isabella claimed that parts of Africa and Guinea belonged to Castile by right and incited Castilian merchants to sail to them.

Afonso found fewer supporters in Castile than he expected and changed his plans, preferring to instead consolidate his control in the area closest to Portugal, in particular Toro, a city that received him favourably even though the garrison of the castle proclaimed itself loyal to Isabella.

In February 1476, the Portuguese army, reinforced by troops brought by John II of Portugal, son of Afonso V, left its base in Toro and surrounded Ferdinand in Zamora.

Bury: "After nine months, occupied with frontier raids and fruitless negotiations, the Castilian and Portuguese armies met at Toro... and fought an indecisive battle, for while Afonso was beaten and fled, his son John destroyed the forces opposed to him...."[13] Publicists from both sides claimed victory.

Alfonso de Palencia, official chronicler of Isabella, narrates an expedition in which two caravels from Palos captured 120 Africans and sold them as slaves.

[19] The preparations were also delayed by a naval battle that took place when the Castilians found out that one or two Portuguese ships with a rich cargo had left the Mediterranean to return to Portugal under the escort of the pirate Alvar Méndez.

In August, negotiations began in Tudela, which culminated with the signing of an accord by which the belligerent parties of the Navarrese Civil War put an end to their conflict.

On August 7, this fleet encountered five armed merchant ships from Cadiz heading for England: three Genoese carracks, a galley, and a Flemish vessel.

[24] After their strategic victory at the battle of Toro, the repulsion of the French attack, and the truce with Afonso V, Isabella and Ferdinand were in a powerful position to obtain the throne of Castile.

Throughout 1476, supporters of Joanna from the nobility continued to submit to Isabella and Ferdinand, particularly those from the Pacheco-Girón lineage: Juan Téllez-Girón and his brother Rodrigo; Luis de Portocarrero; and, in September, the Marquis of Villena.

[25][page needed] Through skilful negotiations, the Queen managed to take control of the main strongholds of Seville occupied by the Marquis and the Duke and, instead of returning them to their legitimate owners, named others as their heads.

[26] The first son of the monarchs, John of Aragon and Castile, was born in Seville on June 30, 1478, which opened new possibilities for dynastic stability of the Isabellian side.

[22] At the beginning of 1478, the monarchs prepared two new expeditions from the port of Sanlúcar de Barrameda, one directed towards Elmina and the other, consisting of at least 35 ships, with the aim of conquering the island of Gran Canaria.

[30] Towards the end of 1478, before word of the defeat at Elmina arrived in Castile, an embassy from King Louis XI of France offered a peace treaty to Isabella and Ferdinand.

It was signed in Guadalupe and included the following clauses:[31] Towards the end of 1478, some of Joanna's supporters revolted in Extremadura, La Mancha (Marquis of Villena), and Galicia.

His objective was to occupy and reinforce the strongholds of Mérida and Medellín, controlled by Beatriz Pacheco, Countess of Medellin and supporter of Afonso V. According to Palencia, the Portuguese army was composed of about 1,000 Knights (of which 250 were Castilians), plus infantry.

On February 24, near the hill of Albuera, the army was challenged by Isabellian forces commanded by Alonso de Cárdenas, Master of the Order of Santiago.

The nuncio Jacobo Rondón de Seseña arrived at Castile with notice that Pope Sixtus IV had reversed himself and had annulled the dispensation previously awarded to Afonso V for his marriage to his niece Joanna.

In April 1479, King Ferdinand arrived at Alcántara to participate in peace talks organized by Beatrice, daughter of Afonso V and aunt of Isabella of Castile.

Isabella and Ferdinand launched an offensive against Alfonso Carrillo de Acuña, Archbishop of Toledo, who was forced to surrender, which allowed the monarchs to challenge the Marquis of Villena.

Joanna la Beltraneja renounced all her Castilian titles, and was given the option of either marrying the heir of Isabella and Ferdinand, Prince John, or retiring to a convent.