John IV of Portugal

The Acclamation of the King John IV, Veloso Salgado, 1908.

Panel of glazed tiles by Jorge Colaço (1940), representing the acclamation of King John IV of Portugal, in 1640. Ponte de Lima, Portugal

When Philip II of Portugal (III of Spain) died, he was succeeded by his son Philip III (IV of Spain), who had a different approach to Portuguese issues. Taxes on the Portuguese merchants were raised, the Portuguese nobility began to lose its influence and government posts in Portugal were increasingly occupied by Spaniards. Ultimately, Philip III tried to make Portugal a Spanish province, meaning Portuguese nobles stood to lose all of their power.

This situation culminated in a revolution organized by the nobility and the bourgeoisie, executed on 1 December 1640, fifty-nine years after the accession of Philip II of Spain to the throne of Portugal. A plot was planned by several associates, known as the Forty Conspirators, who killed the Secretary of State, Miguel de Vasconcelos, and imprisoned the king's cousin, Margaret of Savoy, the Vicereine of Portugal, governing the country in the King's name. Philip's troops were at the time fighting the Thirty Years' War and also dealing with a revolution in Catalonia which severely hampered Spain's ability to quash the rebellion.

Within a matter of hours and with popular support, John, then the 8th Duke of Braganza, was acclaimed as King John IV of Portugal (as legend goes, with the persuasion of his wife) claiming legitimate succession through his grandmother Catherine, Duchess of Braganza.[6] The ensuing conflict with Spain brought Portugal into the Thirty Years' War as, at least, a peripheral player. From 1641 to 1668, the period during which the two nations were at war, Spain sought to isolate Portugal militarily and diplomatically, and Portugal tried to find the resources to maintain its independence through political alliances and maintenance of its colonial income.

His accession led to a protracted war with neighbouring Spain, a conflict known as the Portuguese Restoration War, which ended with the recognition of Portuguese independence in a subsequent reign (1668). Portugal signed lengthy alliances with France (1 June 1641) and Sweden (August 1641) but by necessity its only contributions in the Thirty Years' War were in the field against Spain and against Dutch encroachments on the Portuguese colonies.

The period from 1640 to 1668 was marked by periodic skirmishes between Portugal and Spain, as well as short episodes of more serious warfare, much of it occasioned by Spanish and Portuguese entanglements with non-Iberian powers. Spain was involved in the Thirty Years' War until 1648 and the Franco–Spanish War until 1659, while Portugal was involved in the Dutch–Portuguese War until 1663. In Spain, a Portuguese invasion force defeated the Spanish at Montijo, near Badajoz, in 1644.

Abroad, the Dutch took Portuguese Malacca (January 1641), and the Sultan of Oman captured Muscat (1650). Nevertheless, the Portuguese, despite having to divide their forces among Europe, Brazil and Africa, managed to retake Luanda, in Portuguese Angola, from the Dutch in 1648 and, by 1654, had recovered northern Brazil, which effectively ceased to be a Dutch colony. This was countered by the loss of Portuguese Ceylon (present day Sri Lanka) to the Dutch, who took Colombo in 1656.