Lavalle, Juan (hwän läväˈyā) [key], 1797–1841, Argentine general, governor of Buenos Aires province (1828–29). He served (1816–24) in the War of Independence and (1826–28) in the war with Brazil. Returning to Buenos Aires, he led his troops in revolt (Dec. 1, 1828) against the governor, Manuel Dorrego, who fled. Lavalle was proclaimed governor. He pursued Dorrego, defeated him, and ordered his summary execution (Dec. 13, 1828). The Argentine provinces protested; a national convention pronounced the execution high treason. Forces commanded by Estanislao López, governor of Santa Fe, and Juan Manuel de Rosas defeated Lavalle (Apr., 1829), who took refuge in Montevideo. Aided by Argentine exiles there and, for a time, by French officials, Lavalle organized an army in 1839 and, invading Argentina, campaigned against Rosas. The campaign was generally unsuccessful; Lavalle was decisively defeated by Manuel Oribe, an ally of Rosas, in 1841. He was killed in Jujuy when attempting to reach Bolivia.
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