He began his military career at the end of the 18th century by joining the militia, and later, in 1777, the Prince's Cavalry Regiment. Notwithstanding his military career, he continued taking care of the family business, and was considered one of the wealthiest men in Chile. His family was a member of the highest Aristocracy of the colony, and because of that, he was elected on 18 September 1810 as a member of the First Government Junta of Chile, in spite of his personal sympathy for monarchism. This event propelled him into a very active political participation.