After the death of King Henry IV of Castile in late 1474, the supporters of his reputed daughter, Joanna 'la Beltraneja', waged a war for the succession to the Crown of Castile against the supporters of his half-sister, Isabella, who prevailed by 1479. The war had a marked international character, as Isabella was married to Ferdinand, heir apparent to the Crown of Aragon, while Joanna married her uncle King Afonso V of Portugal at the suggestion of her supporters. France intervened in support of Portugal, as they were rivals with Aragon for territory in Italy and Roussillon.
Despite a few initial successes by the supporters of Joanna, a lack of military aggressiveness by Afonso V and the stalemate 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. The newly gained prestige was used to win municipal support from their allies ..." (Marvin Lunenfeld).
The war between Castile and Portugal alone continued. This included naval warfare in the Atlantic, which became more important: a struggle for maritime access to the wealth of Guinea (gold and slaves). In 1478, the Portuguese navy defeated the Castilians in the decisive Battle of Guinea.
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. Joanna lost her right to the throne of Castile and remained in Portugal until her death.
This conflict has also been called the Second Castilian Civil War, but this name may lead to confusion with the other civil wars that involved Castile in the 14th and 15th centuries. Some authors refer to it as the War of Portugal; however, this name clearly represents a Castilian point of view and implicitly denies Joanna's claim. At other times the term Peninsular War has been used, but it is easily confused with the Peninsular War of 1808–1814, part of the Napoleonic Wars. Some authors prefer the neutral expression War of 1475–1479.
Background
Succession to Crown of Castile
Joanna, born in 1462, was the only child born to King Henry IV of Castile and was called Princess of Asturias as heir presumptive to the throne. A rumour spread that she was not actually the daughter of King Henry but rather of Beltrán de la Cueva, the alleged lover of Henry's wife, Joan of Portugal. Joanna was thus nicknamed "la Beltraneja", as a mocking reference to her assumed father. Pressure from members of the nobility forced the King to strip her of the title and name his half-brother Alfonso as heir presumptive in 1465.
In June 1465, a group of nobility assembled in Ávila, deposed King Henry in effigy and declared Alfonso the king of Castile. In 1467, the rebels were defeated by Henry at Olmeda but the death of Alfonso in 1468 aroused suspicions and increased tensions among the nobles who now favored the accession of Henry's half-sister, Isabel of Castile.
The resulting dispute between supporters of Joanna and Isabella was resolved with the Treaty of the Bulls of Guisando, which gave Isabella succession rights but restricted her marriage options. Nevertheless, Isabella secretly married Ferdinand in 1469 at the age of 17, ignoring Henry IV's wishes.
Gradually, the couple gained a larger number of supporters and obtained a papal bull sanctioning their marriage from Pope Sixtus IV in 1472 and gained the support of the powerful Mendoza family in 1473.
When Henry IV died in December 1474, both candidates for the throne were proclaimed Queen of Castile by their respective supporters. Aware of their position of weakness against Isabella's supporters, Joanna's supporters proposed for the 43-year-old King Afonso V of Portugal, a widower for some 20 years, to marry Joanna, his niece, and assume the throne of Castile with her.
International alliances
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. In June 1474, French troops invaded Roussillon and the Aragonese were forced to retreat. 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.
France was simultaneously at war with the Duchy of Burgundy. That made Burgundy into theoretical allies of Isabella's supporters, but in practice, it continued its war against France without coordinating their actions with the Isabella alliance.
The Kingdom of England was also briefly at war with France with the disembarkation of King Edward IV in Calais in June 1475, but by a quick diplomatic response, Louis negotiated peace with Edward and signed the Treaty of Picquigny in August. Edward IV accepted a truce of nine years, in exchange for significant economic compensation, and returned to England.
The Kingdom of Navarre was experiencing an intermittent civil war, and the Muslim Kingdom of Granada remained neutral despite Portuguese efforts to draw it into the war.
Rivalry between Castile and Portugal in the Atlantic
Throughout the 15th century, merchants, explorers, and fishermen of Portugal and Castile had been penetrating further into the Atlantic Ocean. The possession of the Canary Islands was a point of contention between the two Crowns. Later on, the control of commerce with the territories of Guinea and Elmina, rich in gold and enslaved people, grew to a dispute of even greater importance.
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. Portugal opposed Castilian authority on the islands and continued the exploration of Guinea, with significant commercial benefits.
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. They gave Portugal commercial control and ample religious authority over all of Guinea, and in areas "further beyond". The Holy See did not arbitrate the question of the Canaries, whose conquest had been left relatively suspended. The King of Portugal adopted a freer commercial policy that allowed foreign subjects to trade on the African coasts, in exchange for taxes.
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. That initiated a naval war in the Atlantic.
Conflict
Combatants in 1475
In favour of Joanna:
In favour of Isabella:
The Duchy of Burgundy and the Kingdom of England were at war with France in 1475, but they did not coordinate their actions with the supporters of Isabella and so are rarely considered part of the Isabella alliance.
Fight for throne (May 1475 – September 1476)
Afonso V enters Castile
A Portuguese army entered the territory of the Crown of Castile under the command of Afonso V on May 10, 1475, and advanced to Plasencia, where Joanna was expecting him. Joanna and Afonso were proclaimed sovereigns of Castile on May 25 and were married; the required Papal dispensation (Joanna was Afonso's niece) arrived a few months later. From Plasencia, they marched to Arévalo, with the intention of heading towards Burgos. There, Afonso hoped to be able to unite with any troops sent by his ally, Louis XI of France.
The castle of Burgos and the cities of Plasencia and Arévalo were controlled by the Estúñiga family, supporters of Joanna. The city of Burgos, controlled by the Fernandez de Velasco family, backed Isabella.
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. Zamora and other Leonese villages of the lower Douro also accepted him.
In La Mancha, Rodrigo Tellez-Giron, the Master of the Order of Calatrava, supporter of Joanna, conquered Ciudad Real. Rodrigo Manrique, treasurer of that same Order and the Master of the Order of Santiago, reconquered the city for Isabella.
Ferdinand concentrated an army in Tordesillas, and on July 15, he ordered it to march to seek an encounter with Afonso. Four days later, they arrived at Toro, where the King of Portugal avoided direct combat. Ferdinand, lacking the necessary resources for a prolonged siege, was forced to return to Tordesillas and disband his army. The castle of Toro surrendered to Afonso V, who returned to Arévalo to wait for the expected French intervention.
Rodrigo Alfonso Pimentel, Count of Benavente and supporter of Isabella, situated himself with a small force in Baltanás to monitor the Portuguese. He was attacked on November 18, 1475 and was defeated and imprisoned. Even though this victory opened the way to Burgos, Afonso V decided once again to withdraw, now to Zamora. His lack of aggressiveness debilitated the Joanna alliance in Castile, which began to disintegrate.
Isabellian counterattack
Supporters of Isabella counterattacked by taking Trujillo and gaining control of the lands of the Order of Alcántara, a significant portion of those of the Order of Calatrava, and of the Marquisate of Villena. On December 4, part of the garrison in Zamora rebelled against King Afonso, who was forced to flee to Toro. The Portuguese garrison maintained control of the castle, but the city received Prince Ferdinand the following day.
In January 1476, the castle of Burgos surrendered to Isabella by a pact that avoided reprisals against the defeated.
Battle of Toro
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. The siege took a worse toll on the Portuguese than on those under siege because of the Castilian winter, and on March 1, Afonso V withdrew back towards Toro. Ferdinand and his troops launched a pursuit and caught up to the Portuguese one league (about 5 km) from Toro, and combat began.
After three hours of fighting interrupted by rain and nightfall, the King of Portugal withdrew to Castronuño with part of his troops. His son, John, remained near Toro, retreating with his army in an organized fashion towards the city and even taking a few enemy prisoners. As summarized by Irish scholar John B. 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...."
Publicists from both sides claimed victory. Politically, the battle was decisive because subsequently the bulk of the Portuguese troops retreated back to Portugal along with Joanna, whose side now had hardly any troops in Castile.
War at sea
One of the objectives of Isabella and Ferdinand was to challenge Portugal's monopoly on the rich Atlantic territories of Guinea. The gold and purchased slaves constituted an important source of income which could be used to finance the war, and therefore expeditions to Guinea became a priority for both belligerent sides.
Portuguese ships had transversed the Andalusian coast, apprehending fishing and merchant ships, since the start of the war. To stop this, Isabella and Ferdinand sent four galleys under the command of Álvaro de la Nava, who stopped the Portuguese incursions and plundered the Portuguese city of Alcoutim on the Guadiana River.
Sailors from Palos de la Frontera pillaged the coasts of Guinea. Alfonso de Palencia, official chronicler of Isabella, narrates an expedition in which two caravels from Palos captured 120 Africans and sold them as slaves. Despite protests by the monarchs, shortly afterwards another fleet of three caravels captured an African king and 140 nobles of his village.
In May 1476, Isabella ordered the liberation of the "King of Guinea" and his entourage. The order was only partly obeyed, as the king was liberated and returned to Guinea, but his companions were all sold as slaves.
In 1476, a Portuguese fleet of twenty ships commanded by Fernão Gomes set sail towards Guinea to attempt to regain control there. The King of Castile ordered the preparation of a fleet to apprehend the Portuguese and appointed Carlos de Valera to command. He had numerous problems preparing the expedition, because he was opposed by the Marquis of Cadiz, the Duke of Medina Sidonia, and the Estuñiga family.
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. A fleet of five galleys and five caravels captained by Carlos de Valera and Andrés Sonier intercepted them in Sanlúcar de Barrameda, and were victorious after a hard-fought battle.