War of the Pyrenees
Born into a noble family in San Sebastián in 1778, Pedro Agustín Girón's father was Jerónimo Girón-Moctezuma, 3rd Marquis de las Amarilas and his mother Isabel de las Casas y Aragorri. He was a tenth generation descendant of Aztec Emperor Moctezuma II. He became an official of the "Guardia Real" and participated in the War of the Pyrenees in the Army of Catalonia, in which his father was a high-ranking general.