Originally a bodyguard of Charles V of Spain, he was sent to Mexico to counterbalance the influence of the leader of the Spanish conquest of the Aztec Empire, Hernán Cortés, since the King worried he was becoming too powerful. As Governor of Pánuco, Guzmán cracked down hard on the supporters of Cortés, stripping him and his supporters of property and rights. He conducted numerous expeditions of conquest into the northwestern areas of Mexico, enslaving thousands of Indians and shipping them to the Caribbean colonies. In the resulting power struggles where he also made himself an enemy of important churchmen, Guzmán came out the loser.
In 1537, he was arrested for treason, abuse of power and mistreatment of the indigenous inhabitants of his territories, and he was sent to Spain in shackles. His subsequent reputation, in scholarship and popular discourse, has been that of a cruel, violent and irrational tyrant. His legacy has partly been colored by the fact that history was written largely by his political opponents such as Hernán Cortés, Juan de Zumárraga and Vasco de Quiroga.
Nuño Beltrán de Guzmán was born ca. 1485 in Guadalajara, Spain, to an old noble family. His father was Hernán Beltrán de Guzmán, a wealthy merchant and a High Constable in the Spanish Inquisition; his mother was Doña Magdalena de Guzmán. The Guzmán family supported Prince Charles in the Revolt of the Comuneros and achieved gratitude of the later Emperor. Nuño Beltrán de Guzmán received some experience in law, but never finished a degree. For a period he and his younger brother served as one of 100 royal bodyguards of Carlos V, and he accompanied the Emperor on a trip to Flanders in 1522, and undertook sensitive diplomatic missions, including one dealing with the Bishop of Cuenca (Spain).