Brigadier John (Juan) Mackenna, Chilean military officer and hero of the Chilean War of Independence, is born in Monaghan, County Monaghan on October 26, 1771. He is considered to be the creator of the Corps of Military Engineers of the Chilean Army.

He is born John MacKenna, the son of William MacKenna of Willville House near Monaghan and Eleanora O’Reilly and, on his mother’s side, a nephew to Count Alejandro O’Reilly. Count O’Reilly takes an interest in the young Mackenna and takes him to Spain where he studies at the Royal School of Mathematics in Barcelona. He also trains in the Royal Military Academy as a Military Engineer between 1785 and 1791.

In 1787 Mackenna is accepted into the Irish Brigade of the Spanish Army, and joins the army fighting in Ceuta in northern Africa, under Lieutenant Colonel Luis Urbina, and is promoted to Second Lieutenant. In 1791 he resumes his studies in Barcelona and acts as liaison with mercenaries recruited in Europe. The following year he is promoted to Lieutenant in the Royal Regiment of Engineers. In the War of the Pyrenees against the French, he fights in Rosselló under General Ricardos and there meets the future liberator of Argentina, José de San Martín. For his exploits in defence of the Plaza de Rozas, he is promoted to captain in 1795.

For the purpose of a new assignment, in October 1796, Mackenna leaves Spain for South America. He arrives in Buenos Aires and then travels to Mendoza and to Chile across the Andes and then to Peru. Once in Lima, he contacts Ambrosio O’Higgins, another Irishman, at that time Viceroy of Perú, who names him Governor of Osorno and puts him in charge of the reconstruction works for the southern Chilean town.

In this capacity, Mackenna convinces the families of Castro, on Chiloé Island, to move to Osorno to found a colony there. He builds the storehouse and two mills, as well as the road between Osorno and present-day Puerto Montt. His successful administration provokes jealousy from Chile’s captain-general Gabriel de Avilés, who fears that Mackenna and Ambrosio O’Higgins will create an Irish colony in Osorno. Both Irishmen are loyal to the Spanish crown, though Mackenna has good relations with O’Higgins’ son Bernardo, the future emancipator of Chile, and is also connected with the Venezuelan Francisco de Miranda and his group of supporters of South American independence. When Ambrosio O’Higgins dies in 1801, Avilés is appointed viceroy of Peru. It takes him eight years to remove Mackenna, O’Higgins’s protégé, from Osorno.

In 1809 Mackenna marries Josefina Vicuña y Larraín, an eighteen-year-old Chilean woman from a family with revolutionary connections, with whom he has three children. After the Declaration of Chilean Independence in 1810, he adheres to the Patriot side and is commissioned by the first Chilean government to prepare a plan for the defense of the country and oversees the equipment of the new Chilean Army. At this juncture he trains the first military engineers for the new army.

The following year Mackenna is called to the defence committee of the new Republic of Chile, and in 1811 is appointed governor of Valparaíso. Owing to political feuds with José Miguel Carrera and his brothers, he is dismissed from the post and taken prisoner. He is a firm ally of Bernardo O’Higgins, who appoints him as one of the key officers to fight the Spanish army of General José Antonio Pareja. His major military honour is attained in 1814 at the Battle of Membrillar, in which the general assures a temporary collapse of the royal forces.

As a reward for his victory, Mackenna is appointed commandant-general by Bernardo O’Higgins, but after a coup d’état led by Luis Carrera he is exiled to Argentina in 1814, when Carrera comes to power. Mackenna dies in Buenos Aires on November 21, 1814, following a duel with Carrera.

A bust of General Mackenna is publicly presented to Monaghan County Museum on August 5, 2004 by his direct descendant, Luis Valentín Ferrada. At the presentation ceremony, MacKenna, the man “unreservedly regarded as the greatest of County Monaghan’s exiles” is commemorated in speeches by Most Rev. Dr. Joseph Duffy, Bishop of Clogher and by his descendant Senor Ferrada who declares, “In this city of Monaghan, very near to Willville House, the tombs of my ancestors are in the old cemetery. There, my own blood is interred in the sacred earth.”