The Year of Isabella I of Castile – The peace treaty with Portugal

From the death of Queen Isabella’s half-brother, King Henry IV of Castile, she had been at war with Portugal.

King Henry IV left one daughter as heiress to the throne, but her legitimacy was questioned. She became known in history as Joanna La Beltraneja for her supposed father, Beltrán de la Cueva. Joanna was sworn in as heiress on 9 May 1462, with Isabella and her brother Alfonso being the first to swear.

However, it appears that several nobles already doubted Joanna’s legitimacy, not in the least because of jealousy towards Beltrán de la Cueva, who held the King’s favour. Isabella later wrote that she knew why some objected to swearing the oath. She wrote, “It was something she [the Queen] had demanded because she knew the truth about her pregnancy and was taking precautions.”¹ Rumours about Beltrán de la Cueva being little Joanna’s biological father were beginning to circulate. It is impossible to tell if Joanna was Beltrán de la Cueva’s daughter, but we know Joan conceived again within the year. Tragically, she lost the child, a boy, at six months.

However, these rumours were the perfect fuel for a rebellion.

Joanna was just two years old when a manifesto of complaints and grievances was issued against King Henry by several nobles. This led to the Representation of Burgos in 1464, where Henry was forced to recognise Alfonso as the legitimate heir.² This was agreed upon with the condition that Alfonso would one day marry Joanna. However, Henry soon reconsidered, and this led to a ceremonial deposition in effigy in 1465, and the 11-year-old Alfonso was crowned as rival King. Meanwhile, Isabella was still at court with Henry and Joan.

Isabella and Alfonso were reunited in 1467 when he triumphantly rode into Segovia as Queen Joan fled. Isabella asked to return to her mother at Arévalo, and at the end of the year, they celebrated Alfonso’s 14th birthday with the three of them. They stayed there until they were forced to flee due to an outbreak of the plague at the end of June 1468. Alfonso fell ill at Cardeñosa, and for four days, he fought for his life. His death was expected, and Isabella wrote, “And you all know that in the moment that the Lord decided to take his life, succession of the kingdoms and royal lands of Castile and Leon will, as his legitimate heiress and successor, pass to me.”³

Alfonso died on 5 July 1468. The battle was now between Joanna and Isabella.

Joanna’s father died on 11 December 1474, and her aunt Isabella successfully claimed the throne of Castile. It is not clear if Joanna and her mother were present when Henry died. After a few more marriage proposals, Joanna was married to her maternal uncle, King Afonso V of Portugal, on 29 May 1475. King Afonso invaded Castile to support Joanna’s claim shortly after their betrothal ceremony on 1 May. Shortly after her marriage, her mother, Joan, also died. Joanna was still only 13 years old, while her aunt was a mature married woman with a daughter of her own. Afonso did not consummate the marriage with his 13-year-old niece as he went to war.

Meanwhile, Joanna sent out letters to the cities and towns of Castile which read, “During his lifetime, he always wrote and swore, both in public and in private, to all those prelates and grandees who asked about it and to many other trustworthy people that he knew me to be his true daughter.”⁴ She also claimed that her father had named her as his heiress on his deathbed and that he had been poisoned by Isabella and her husband, Ferdinand. She called for Isabella to be punished, saying, “You must all rise and join, serving, helping and ensuring that this abominable, detestable action be punished.”⁴

The War of the Castilian succession would continue for four years. After the Battle of Toro in March 1476, Joanna and Afonso left Castile in June. However, troops remained stationed in Castile. Most of the time, Joanna was left in Portugal, and she often went long periods without seeing her husband. However, her exact whereabouts can not always be established.

They soon lost the support of Diego López de Pacheco, 2nd Duke of Escalona, and he “promised to serve them [Isabella and Ferdinand] in public and private from then on with complete faithfulness and loyalty, be it against the Portuguese King, his niece [Joanna], the French, their allies or anyone else.”⁵ Archbishop Carrillo also soon pledged his loyalty to Isabella. Another big blow came on 30 June 1478 when Isabella gave birth to a son named John. To some, the birth of a male heir was the proof that God had chosen Isabella as Queen.

It was Isabella’s aunt, Beatriz of Portugal, Duchess of Viseu (who was also King Afonso’s sister-in-law), who made the first approach for peace. Isabella agreed to meet her at the frontier town of Alcántara. They talked for three days, and Isabella insisted on Joanna being sent to a convent. She also refused to name Joanna as a Princess as “giving her that title is to confess that she is the daughter of a king and queen. And the queen [Isabella] thinks that… this in itself is sufficient reason to stop talking about peace.”⁶ Negotiations dragged on for another six months.

The peace treaty was signed in Alcáçovas (present-day Viana do Alentejo) on 4 September 1479. It was ratified by King Afonso on 8 September, followed by Queen Isabella I and King Ferdinand II on 6 March 1480. It became known as the Treaty of Alcáçovas-Toledo.

One chronicler wrote, “She, with no less grief than her own sadness and with painful lamentations of her own and of all her people, left the title of Queen and took the name of Doña Juana. She stripped her body of the brocades and silks she wore, and they dressed her in the brown habits of St Clare, taking from her the royal crown of Castile and Portugal, with which she was titled, and cutting her hair off like a poor maiden.”⁷

1. Isabella of Castile by Giles Tremlett p.32
2. Due to male-preference primogeniture, Isabella was behind Alfonso in the line of succession/
3. Isabella of Castile by Giles Tremlett p.40
4. Isabella of Castile by Giles Tremlett p.124
5. Isabella of Castile by Giles Tremlett p.146
6. Isabella of Castile by Giles Tremlett p.170
7. Juana de Castilla, mal llamada La Beltraneja by Tarsicio de Azcona p.77