In addition, a betrothal was arranged between Beatrice, Ferdinand I of Portugal's newborn daughter, and Fadrique, created Duke of Benavente, another natural son of King Henry II of Castile.

Once these events were known in the Portuguese court, negotiations began for the betrothal of Beatrice with the first-born son of the new King, the future Henry III of Castile, in order to counter any aspiration of John of Portugal to the throne with the political and military support of the Castilians.

[19] By July 1380, Ferdinand I had changed his politics by secretly allying himself in the Treaty of Estremoz with King Richard II of England and the Duke of Lancaster, defenders of the Petrist cause.

The negotiations for this alliance brought to Portugal a Petrist exile, Juan Fernández de Andeiro, Count of Ourém, who would later have prominent influence at the Portuguese court.

When the Castilian King heard of the agreement thanks to the exiled John of Portugal, he sealed an alliance with France through the Treaty of Vincennes, accepting obedience of his kingdom to the Antipope Clement VII,[20][21] and he undertook the third Fernandine War.

[37] Pedro de Luna, a pontifical legate for the Kingdoms of Castile, Aragon, Portugal and Navarre, solemnized the betrothal at Elvas on 14 May 1383,[38] and the official wedding ceremony took place on 17 May in Badajoz Cathedral.

The marriage contract was taken to the Cortes de Santarém of August and September to swear to accept Beatrice and John I of Castile as heirs of Portugal, although these acts were not conserved.

[33] For her part, Queen Leonor Teles gave birth on 27 September to a daughter who lived only a few days,[39] so Beatrice remained the only legitimate child of King Ferdinand I.

[41][45][46][54][55][56][57][58][59][60][61] John I of Castile decided to lead troops into Portugal to take possession of the Kingdom, against the advice of some members of his Council since it represented a clear contravention of the agreements made in the Treaty of Salvaterra.

[64] Combining opposition to the regent and her Petrist clique,[65] the expectation of a commercial monopoly,[24] and fears of Castilian dominion and loss of Portuguese independence,[34][66][67] uprisings began in Lisbon in late November and early December.

The Master of Aviz killed the Count of Ourém, a favourite of the regent, and after that, there was the uprising of the peasants against the government instigated by Alvaro Pais,[50] in which Martinho Anes, Bishop of Lisbon, was murdered.

The uprising spread to the provinces, claiming the lives of the Abbess of the Benedictine cloister in Évora, the Prior of the collegiate church of Guimarães and Lançarote Pessanha, Admiral of Portugal, in Beja, among others.

The Master of Aviz constituted his own Council in which João das Regras appeared as Chancellor, and requested the aid of England; he also tried to besiege Alenquer, but Leonor fled to Santarém,[73] so he immediately returned to prepare the defence of Lisbon.

In Santarém, Leonor Teles proceeded to recruit an army and sought the help of her son-in-law the King of Castile[74] to defeat the insurgents who didn't accept her regency or recognize her daughter Beatrice as Queen.

[78] After this, many knights and castle governors came to pay homage to him and his wife Beatrice,[62][79][80] such as those of Santarém, Ourém, Leiria, Montemor-o-Velho, Feira, Penella, Óbidos, Torres Vedras, Torres Novas, Alenquer, Sintra, Arronches, Alegrete, Amieira, Campo Maior, Olivenza, Portel, Moura, Mértola, Braga, Lanhoso, Valença do Minho, Melgaço, Vila Nova de Cerveira, Viana do Castelo, Ponte de Lima, Guimarães, Caminha, Bragança, Vinhais, Chaves, Monforte, Miranda do Douro, Montalegre, Mirandela, Castelo Rodrigo, Almeida, Penamacor, Guarda, Covilhã and Celorico da Beira, among others.

[85] Although he counted on the support of the majority of the Portuguese aristocracy,[11][69][86][87][88] King John I couldn't repeat the Castilian triumphs of the Fernandine Wars and failed before Coimbra and Lisbon.

He took over the region north of the Duero where Portuguese knights still maintained fidelity to Beatrice and John I of Castile:[83] Villareal de Pavões, Chaves and Bragança capitulated in late March 1386,[92] and Almeida in early June.

Throughout these struggles, they preserved the dispositions King John I had made in his testament, written at Celorico da Beira in 1385,[96] that provided for the economic maintenance of the household of the now-Dowager Queen Beatrice, on which depended the Portuguese exiles who had followed her to Castile.

[98] The dynastic rights of Beatrice would for decades constitute an insurmountable obstacle to the normalization of relations between the Kingdoms of Castile and Portugal, a situation that could only be completely resolved in 1431 after the signing of the Treaty of Medina del Campo.

During the reign of Henry III there was a greater Portuguese exodus to Castile, the common factor of which was the rejection of the House of Aviz, and the Castilian King granted the exiles some compensation for their losses in Portugal.

In the negotiations that culminated in the truce of 1402, the Castilians persisted in maintaining the rights of Beatrice and proposed a marriage between her and Afonso, the first-born son of John I of Portugal, but this union was rejected by the Portuguese king.

Ferdinand still maintained the superiority and legitimacy of his family's dynastic rights, but in the negotiations that developed into the provisional treaty of 1411,[100] the dynastic question and the Western Schism remained separate from the settlement in other points of friction: the Castilians promised not to wage war with Portugal for Beatrice's rights or the Western Schism, and agreed to suppress any claims by the exiles faithful to Beatrice over their confiscated property or indemnifications prior to the year 1402.

The new elected Pope, Martin V, recognized the King of Portugal, and thus in the bull Sane Charissumus of April 1418 he asked the Christian sovereigns to help the Portuguese monarch in his fight against the Saracens.

Following her marriage, rather than including territorial incomes, the dowry of the princess consisted of money that King John I of Castile had to accept with the prospect of obtaining the Kingdom of Portugal.

As Queen consort of Castile, she maintained her household, in which Juan Rodríguez Portocarrero served as First Mayordomo, and her Chancellor was the Bishop of Guarda, Afonso Correia, who would be succeeded by the lawyer Vicente Arias de Balboa.

Although as the wife of the Castilian King, she had jurisdiction over Tordesillas, San Esteban de Gormaz, Cuéllar, Peñafiel, Medina del Campo and Olmedo, when she became a widow she only retained Béjar and Valladolid.

She rejected it since it would have led to the loss of her Castilian patrimony, which would have harmed her Portuguese exile partisans, and she needed to retain the ability to make the type of political marriage that would have been necessary for a hypothetical return to Portugal.

In 1419 Beatrice sent Juan González de Sevilla, professor of the University of Salamanca and later Bishop of Cádiz, to appeal to Pope Martin V asking for the type of permissions usually granted to a person preparing to die.

No documentary evidence of her death has survived, but her properties were dispersed, granted to the constable Álvaro de Luna from 1420, and in June 1420 Toro appears to have reverted to the Crown.

Many Portuguese nobles of the pro-Castillian faction also recognized her husband, King John I of Castile, as their jure uxoris monarch, rendering him vassalage and obedience, as, for example, did Lopo Gomes de Lira in Minho.