Portuguese succession crisis of 1580

The Portuguese succession crisis of 1580 (Crise de sucessão de 1580) emerged as a result of the deaths of young King Sebastian I of Portugal in the Battle of Alcácer Quibir in 1578 and his successor and great-uncle Henry I in 1580. As Sebastian and Henry lacked immediate heirs, a dynastic crisis unfolded, marked by internal conflicts and external contenders vying for the Portuguese throne. Ultimately, Philip II of Spain succeeded Henry I as King of Portugal, uniting the Portuguese and Spanish Crowns in the Iberian Union. This personal union endured for 60 years, during which the Portuguese Empire faced decline and global challenges, notably the Dutch–Portuguese War.

The Cardinal-King
After the disastrous Battle of Alcácer Quibir in 1578, the Cardinal Henry, Sebastian's grand-uncle, succeeded him as king. Henry renounced his clerical offices and sought to take a bride for the continuation of the Aviz dynasty, but Pope Gregory XIII, affiliated with Philip II, did not release him from his vows. In January 1580, when the Cortes were assembled in Almeirim to decide upon an heir, the Cardinal-King died and the Regency of the Kingdom was assumed by a Council of five members.

Claimants to the throne
By this time the Portuguese throne was disputed by several claimants. Among them were: The descendants of the Duchess of Braganza obtained the throne in 1640 (in the person of her grandson John IV of Portugal), but in 1580, she was only one of several possible heirs. The heir by primogeniture was her nephew Ranuccio Farnese, being the son of Catherine's late older sister Maria, followed by his siblings; then the Duchess herself and her children; and only after them, King Philip. Philip II was a foreigner (although his mother was Portuguese) and descended from Manuel I by a female line; as for Anthony, although he was Manuel I's grandson in the male line, he was of illegitimate birth.

The heir by primogeniture, 11-year-old Ranuccio Farnese, Hereditary Duke of Parma and Piacenza, was the grandson of Infante Duarte of Portugal, the only son of Manuel I whose legitimate descendants survived at that time. However, his father Alessandro Farnese, Duke of Parma was an ally of the Spanish king, another contender, so Ranuccio's rights were not claimed at that time. Ranuccio became reigning Duke of Parma in 1592.

Instead, Ranuccio's maternal aunt Catherine, Duchess of Braganza, asserted her claim as the daughter of Infante Duarte. Catherine was married to João I, Duke of Braganza (descendant in male line from Afonso I, Duke of Braganza, an illegitimate son of King John I of Portugal), who himself was grandson of the late Duke Jaime of Braganza, also a legitimate heir of Portugal, being the son of Infanta Isabella, sister of Manuel I and daughter of Infante Ferdinand, Duke of Viseu, second son of King Duarte I. The duchess also had a son, Dom Teodósio de Braganza, who would be her royal heir and successor to the throne. Catherine's relatively strong claim was bolstered by her residency in Portugal. Although she was Henry's preferred successor, her bid for queenship ultimately failed due to her sex, the powerful influence of Philip II, and the unpopularity of her husband.

According to primogeniture, the line of succession of the Portuguese throne would have been:
 * 1) Ranuccio Farnese, Hereditary Duke of Parma and his siblings Odoardo and Margherita
 * 2) Infanta Catherine, Duchess of Braganza and her children
 * 3) Philip II of Spain and his children
 * 4) Maria of Austria, Holy Roman Empress, Philip's sister, and her children
 * 5) Emmanuel Philibert, Duke of Savoy and his children (son of Beatrice of Portugal, Duchess of Savoy, daughter of Manuel I)

Genealogical summary
Claimants following King Henry I's death (1580)



Other Claimants
Catherine de' Medici, Queen mother of France, used a claimed descendance from King Afonso III of Portugal from his first marriage with Matilda, Countess of Boulogne to advance with a claim to the Portuguese Throne. Her claim was likely only presented to entice Philip to offer compensation for its withdrawal. She later aided António, providing him with a French fleet.

The Pope, at the time Gregory XIII, also had a claim to the Portuguese Throne, since King Henry was a Cardinal and the inheritance of all cardinals reverts to the Church. The pope claimed it was his right to have the Kingdom of Portugal, as well as a property that had belonged to the King.

Neither claim was seriously considered.

António of Portugal and Philip of Spain
António, Prior of Crato (1531–1595) was a claimant of the Portuguese throne during the 1580 crisis and, according to some historians, King of Portugal (during a short time in 1580 in mainland Portugal, and since then until 1583, in the Azores). António was the illegitimate son of Infante Luis (1506–1555), and therefore grandson of King Manuel I. It was precisely because of his illegitimacy that his claim to the throne was weak and considered invalid.

Philip II of Spain managed to bring the aristocracy of the kingdom as support to his side. For the aristocracy, a personal union with Spain would prove highly profitable for Portugal at a time when the state finances were suffering. António tried to seduce the people for his cause, comparing the present situation to that of the Crisis of 1385. Then—just as in 1580—the king of Castile had invoked blood descent to inherit the Portuguese throne; and the Master of Aviz (John I), illegitimate son of King Peter I, asserted his right to the throne at the Battle of Aljubarrota, which ended in a victory for John's troops, and in the Cortes of Coimbra in 1385.

In June 1580, António proclaimed himself King of Portugal in Santarém, followed by acclamation in several locations throughout the country. His domestic government lasted until 25 August 1580, when he was defeated in the Battle of Alcântara by Habsburg armies led by the Duke of Alba. After the fall of Lisbon, he purported to rule the country from Terceira Island, in the Azores, where he established a government in exile until 1583. Some authors consider António the last monarch of the House of Aviz (instead of Cardinal-King Henry) and the 18th King of Portugal. His government in Terceira island was only recognized in the Azores, whereas on the continent and in the Madeira Islands power was exercised by Philip II, who was acclaimed king in 1580 as Philip I of Portugal and recognized as official king by the Cortes of Tomar in 1581. The new king's election was carried on condition that the kingdom and its overseas territories should remain separate from Spain and keep their own laws and Cortes.

After his defeat in the Azores, António went into exile in France—traditional enemy of the Habsburgs—and courted the support of England. An invasion was attempted in 1589 under Sir Francis Drake—leading the so-called English Armada—but ended in failure. António continued to fight until the end of his life for his rights to the throne.

Consequences
The matter of whether Portugal was actually invaded by Spain is contested. Philip II had a legitimate claim to the throne, but as with many other dynastic struggles of the age, it was shrouded in controversy. In any case, the Habsburg kings maintained Portugal's status and gave excellent positions to Portuguese nobles in the Spanish Court, and Portugal maintained an independent law, currency and government. However, Portugal saw its wealth and "cultural individuality" gradually decreasing. Portuguese colonies came under sustained attack from their enemies, especially the Dutch and English.

Sixty years after these events, John II, Duke of Braganza (1603–1656) accepted the throne offered by the Portuguese nobility, who had become frustrated under Habsburg rule, becoming John IV of Portugal. He was the grandson of Catherine, Duchess of Braganza, who had in 1580 claimed the Portuguese crown, and son of Teodósio II, Duke of Braganza (who died insane in 1630). John was raised to the throne of Portugal (of which he was then held to be the legitimate heir) during the Portuguese Restoration War against King Philip IV of Spain.

There were many impostors who claimed to be King Sebastian, variously in 1584, 1585, 1595, and 1598. "Sebastianism", the legend that the young king would return to Portugal on a foggy day persisted for years, and was even strong into the 1800s.