MENDOZA, Pedro de, soldier, born 'in Cadiz, Spain, about 1487; died at sea in 1536. He was a wealthy gentleman of Cadiz, belonging to a distinguished family, and, while holding a post at the court, made an offer to Charles V., in 1534, to complete, at his own expense, the discovery and conquest of Paraguay and the countries on the Rio de la Plata, and extend the Spanish explorations to the southern extremity of South America. He was named by this monarch adelantado, or military chief, of these countries, and sailed, 24 August, 1534, with fourteen vessels and 3,000 men. The emperor had given him 2,000 ducats, and advanced ., 000 more, on condition that he should transport to the new country, within two years, a thousand colonists and a hundred horses, build a road to the Pacific ocean, erect three forts, and take with him eight monks, a physician, a surgeon, and an apothecary; but he was forbidden to introduce a lawyer into the colony. Mendoza was made hereditary chief judge and constable of the countries that he should discover, and given the right to retain half the treasures of the caciques who might be killed in the wars that he should wage, with nine tenths of the ransoms of prisoners. He landed on the coast of Brazil, after a terrible tempest had dispersed the fleet, where, falling sick. He intrusted the command of his ships to Juan de Osorio, his lieutenant. Having had reason to suspect this of-ricer of treachery, he caused him to be assassinated a short time afterward. As soon as Mendoza recovered he continued his voyage, sailed up the Rio de la Plata as far as the island of Saint Gabriel, reconnoitred the southern coast opposite, and founded there the city of Buenos Ayres, 2 February, 1535, with two forts to defend it. Soon after the arrival of the expedition the provisions began to fail, and the aborigines attacked the foraging parties that were sent in quest of supplies. The Querandis, a tribe numbering about 3,000, at first furnished them with food, but, in consequence of ill treatment, ceased to frequent the camp. Don Diego, a brother of the commander, led a force against them, but was killed with more than two thirds of his men. After this the colonists were attacked by the Querandi Indians frequently, but repelled them till, in December, 1535, the new city was captured by the Indians and burned. Mendoza retired to the fort of Sanctus-Spiritus, whence he despatched Juan de A volas (q. v.) to explore the upper course of the river. Disheartened by his failure, he sailed in the summer of 1536 for Spain and died during the long voyage.