Dom Sebastian, king of Portugal, born in Lisbon, Jan. 20, 1554, killed in battle in Africa, Aug. 4, 1578. He succeeded his grandfather John III. in 1557, and in his 21st year undertook with 800 or 900 soldiers an expedition against Tangier, the result of which encouraged him to still greater effort. The war raging in Morocco between Muley-Malek and his nephew Muley-Mohammed, the latter of whom had been deprived of the throne by the former, seemed to offer a favorable opportunity for the Portuguese monarch to interfere. With a large fleet, having on board 15,-000 or 20,000 soldiers, he sailed to Africa to support the cause of the nephew in 1578. He found Muley-Mohammed at Tangier, but the landing of his forces took place at Azila, where he was joined by Muley-Mohammed with his forces, and together they began the campaign by the siege of Alcazar. Muley-Malek, who had collected an immense army, gave battle, Aug. 4. After a desperate engagement, in which Sebastian displayed great heroism but no generalship, his army was routed and almost all killed or taken prisoners; and he himself disappeared, but his dead body is said to have been recognized on the field by a page.
Muley-Mohammed was drowned in the flight, and Muley-Malek, who had risen from his sick bed to participate in the action, died, so that all the chiefs perished. The flower of the Portuguese nobility was destroyed in this expedition, and Portugal, becoming a prey to anarchy, soon fell into the power of Spain. But the Portuguese could not believe that their king had been killed, and many adventurers sprung up who gave themselves out as the true Sebastian. Among these impostors the most remarkable was one who appeared in Venice 20 years after the battle, and asserted that he was left upon the field among the dead and wounded; that he had remained in Barbary, finally took the resolution of disclosing himself to the pope, on the way was plundered by robbers, and was recognized by a few Portuguese and taken to Venice. The senate of that city banished him, and on his return imprisoned him; but his case excited universal sympathy in Europe, and he was finally set at liberty. He was imprisoned again at Florence, then taken to Naples, and, insisting upon his statements, was treated as a galley slave.