History of the Catholic Church
Catharism  grew in Languedoc in the 12th-century.  The Inquisition originated during the period of struggle against this heresy. After the Cathars were accused of murdering a papal legate in 1208, Pope Innocent III declared the Albigensian Crusade. Abuses committed during the crusade caused Innocent III to informally institute the first papal inquisition to prevent future massacres and root out the remaining Cathars. Formalized under Gregory IX, this Medieval inquisition executed an average of three people per year for heresy at its height. Over time, other inquisitions were launched by the Church or secular rulers. Its main objectives were to prosecute heretics, to respond to the threat of Moorish invasion or for political purposes. The accused were encouraged to renounce their heresy and those who did not could be punished by penance, fines, imprisonment or execution by burning.