During his stage as a seaman, he travelled all around the Atlantic, the Mediterranean and America. He was the first Galician viceroy in America that did not have a noble title. He was a war seaman and arrived in America in 1765 taking part of an expedition to the Falkland Islands, where he became a governor (1774-79). Carlos III nominated him as viceroy of Nueva Granada (Colombia, Ecuador and Venezuela) for his knowledge on the matters of South America. Before arriving in Bogotá to take up his post, he was nominated as viceroy of Peru, which was the most important viceroyalty in America, although he preferred the viceroyalty of Nueva Granada. He promoted the Spanish explorations in the Pacific and the South of Chile. He founded the first newspaper of South America ('El Mercurio Peruano') and promoted the studies on Anatomy. He also founded the Academy of Nautics in Lima and a laboratory to take profit of the metals, the great wealth of Peru. When he ceased his functions, he was elected member of the High War Council and some years later director general of the Army and minister of the Navy.