Hugo O'Connor, born in 1732 in Dublin, Ireland, into the Gaelic-Irish aristocratic O'Connor family, is a descendant of king of Ireland Turlough Mor O'Conor.

For political and religious reasons, when he was eighteen years old—like many other Irish aristocrats—O'Connor had left his homeland and moved to Spain where his cousins Alexander and Dominic O'Reilly, were serving as officers in the Spanish Royal Army; he had been established in Aragon.In his youth he had joined the regiment of Volunteers of Aragon, eventually acquiring the title of major.

During his years in the military, he had been sent to Cuba and Mexico City, where he had distinguished himself by his ability as a military strategist and was appointed captain for the Northern Territory to exercise dominion in the region.

He had gone to Texas to investigate a dispute around San Agustín de Ahumada Presidio between Governor Ángel de Martos y Navarrete and Rafael Martínez Pacheco (future governor of Texas).

It was at this time that he obtained the title of inspector general of the Provincias Internas (general inspector of the Interior Provinces).

Later, in 1767, he had been appointed governor of Texas, in replacement of Martos and Navarrete.

On assuming office, he had found that one of its major cities, San Antonio, had been shattered by frequent attacks of several native tribes.

Therefore, the new governor set up a garrison at Los Adaes to protect the city.

In 1771 he had become commander of the Chihuahua frontier and in January 20, 1773 he had been appointed commandant inspector of presidios under the office of colonel.

He and Governor Juan María Vicencio de Ripperdá had rejected the petition of Antonio Gil Y'Barbo that the settlers be allowed to return to their original homes.

To strengthen the protection of Nueva Vizcaya and Coahuila, O'Connor decides to expel the Apaches in the region, making war against these peoples in 1775 and 1776, killing a large number.

The Apaches who survive flee to more western areas.