Pope Sixtus IV issues a papal bull (Exigit sincerae devotionis affectus) on November 1, 1478, authorizing the Spanish Catholic Monarchs, Ferdinand II of Aragon and Isabella I of Castile, to appoint inquisitors to root out heresy in Spain by enforcing religious orthodoxy among the Jews and Muslims converts.
Sixtus IV was not able to maintain control as the monarchs proceeded treating the institution as a royal, state-run tribunal allowing them to seize confiscated property. This version of the Inquisition replaced the previous Medieval Inquisition (established around 1184) and acted as a powerful instrument of state power, continuing until the 19th century.