John MacKenna (Juan Mackenna, this the normal spelling in Spanish) was a leading figure in the establishment of Chile as an independent nation.
He was born either in Clogher, County Tyrone or in Aghaninimy, County Monaghan, and was educated at the Royal Academy of Mathematics in Barcelona. He was appointed a cadet in the Irish Corps of Military Engineers in the Spanish army. In 1796 he sailed to Peru and served as a military engineer in Chile. In 1797 he was appointed Governor of Osorno. He became Commander-in-Chief of Artillery and Engineers in Carrera's revolutionary organisation. After a disagreement he was banished, but was recalled in 1813, at which point he became military commander of Santiago, having been promoted to brigadier-general. He changed allegiance to Carrera's rival, Bernardo O'Higgins and became second-in-command after O'Higgins's victory. In 1814 Carrera was restored to power and MacKenna was banished. He died the same year in a duel with Carrera's brother in Buenos Aires.
A memorial bust to him was presented to the Monaghan County Museum in 2004.
His grandson was Benjamín Vicuña Mackenna (1831-1886), a distinguished politician and historian in Chile. A cousin, Count (Conde) Alexander (Alejandro) O'Reilly who emigrated to South America from Dublin had a most distinguished career in Spanish America; his grandfather fought at Derry in 1689.
||26 October 1771
||21 November 1814