Final answer:
The Catholic Princes were commanded to persecute heresy through the Inquisition established by Pope Gregory IX, which could involve torture and execution to enforce religious conformity.
Step-by-step explanation:
The command that the Catholic Princes received regarding the hunting of heresy was quite direct and harsh. During the 1230s, Pope Gregory IX instituted an Office of Papal Inquisition to systematically persecute heresy throughout Western Christendom. This period marked the beginning of the Inquisition, which was a long and grueling effort to enforce religious conformity in western Europe through means including torture and execution. Notably, in 1252, Pope Innocent IV authorized the use of torture on suspected heretics, compelling them to either prove their innocence or confess, failing which they could face execution, often by being burned at the stake. Furthermore, the assets of those condemned could be confiscated, which inadvertently encouraged the continuation of these persecutions. This command and the establishment of the Inquisition aimed to impose religious homogeneity in western Europe, ensuring conformity to Catholic doctrine through fear and force.