MACKENNA, Juan, Chilian soldier, born in Clogher, Ireland, 26 October, 1771 ; died in Buenos Ayres, 21 November, 1814. At the age of thirteen he left Ireland by order of his uncle, Count O'Reilly, who destined him for the Spanish military service, entered the Royal academy of mathematics in Barcelona, and in 1787 was appointed cadet in the corps of military engineers. He served during the African campaign in 1787-'8 in the garrison of Ceuta, and later in the campaign of Roussillon against, the French republic, and at first rose rapidly in rank, but afterward, remaining for a long time without promotion as brevet lieutenant-colonel, he thought himself neglected, and determined to seek his fortune in the New World. He obtained leave, and left in 1796 for Peru with warm recommendations from his uncle to the Viceroy Ambrosio O'Higgins, an Irishman, like himself. He was favorably received, and in 1797 appointed civil and military governor of the colony of Osorno, Chili, which place he filled till 1808. In 1809, when an English invasion was threatened, Mackenna, as the most experienced military officer in the country, was commissioned to erect fortifications along the coast, and take the necessary measures of defence, but in 1810, dissatisfied with the Spanish government, he joined the revolutionists, and became an ardent defender of the cause of independence. Early in 1811 he was appointed provisional governor of Valparaiso, and in September of the same year became a member of the governing junta, under the auspices of Jose M. Carrera, and at the same time commander-in-chief of artillery and engineers, with the rank of colonel. By a mutiny that was headed by the brothers Carrera, he lost his place in the government, but retained the command of the artillery, till, as he continued his opposition to Carrera, he was banished to the province of Rioja. In 1813 he was recalled, commissioned to make a strategical map of the republic, and appointed chief of staff for the army of the south, to repel the invasion of Pareja. He assisted in the campaign and was promoted brigadier. On his return to Santiago he was appointed military commander of the city, but when Jose N. Carrera returned to power he was arrested in his bed, thrown into prison, and banished to Mendoza, 14 July, 1814. He then went to Buenos Ayres, and, meeting Carrera's brother Luis, was killed in the duel that resulted from their quarrel.