[7] The dual regency was a failure and in 1439, the cortes named Pedro "protector and guardian" of the king and "ruler and defender" of the kingdom.

[19] The grant caused conflict with John II of Castile, who asserted that conquest of Barbary and Guinea were reserved for the Castilian crown.

[20] John II was also angered by Henry's conduct in the Canary Islands and repeatedly wrote to Afonso complaining about displays of hostility, such as attacks on Castilian shipping.

[22] In 1452, Pope Nicholas V issued the papal bull Dum Diversas, which granted Afonso V the right to reduce "Saracens, pagans and any other unbelievers" to hereditary slavery.

[26] A large crusade was desired but the Papacy struggled to rally the necessary forces and Afonso, having already made war preparations in Portugal, saw an opportunity to pursue military campaigns in Africa.

However, her paternity was questioned; it was rumored that his wife, Queen Joan of Portugal (Afonso's sister) had an affair with a nobleman named Beltrán de La Cueva.

[43] In March 1476, after several skirmishes and much maneuvering, the 8,000 men of Afonso and Prince John, faced a Castilian force of similar size in the Battle of Toro.

[44] The fight was fierce and confusing but the result was a stalemate:[45][46][47] while the forces of Cardinal Mendoza and the Duke of Alba won over their opponents led by the Portuguese king—who left the battlefield to take refuge in Castronuño—the troops commanded by Prince John defeated and persecuted the troops of the Castilian right wing and recovered the Portuguese royal standard, remaining ordered in the battlefield where they collected the fugitives of Afonso.

[50] In September 1477, disheartened that his efforts to secure support had proved fruitless, Afonso abdicated the throne and embarked on a pilgrimage to Jerusalem.

[53] Prince John had been proclaimed king days prior to Afonso's arrival, but relinquished his new title and insisted that his father reassume the crown.

[56] The Treaty of Alcáçovas was finally negotiated in 1479, wherein Afonso renounced his claim to the Castilian throne in exchange for Portuguese hegemony in the Atlantic south of the Canary Islands.

[57][58][59] Although the treaty was advantageous for Portugal, the king was deeply unhappy with the provision that forced his bride and niece, Joanna, into a convent.