According to Innocent III, what actions were French authorities to take against heretics? What reason did he give for taking these actions?

Answer 1

Innocent called for a crusade against the Cathars, a semi-mystical Christian offshoot. They had been tolerated in the southern part of France, with one of the senior noblemen of the area actively protecting them in defiance of Rome's edicts. Innocent's declaration freed those French noblemen who followed the Roman version of Catholicism to essentially invade the southern territories that were strongholds of the Cathars. Participating in the Crusade for at least 40 days gave noblemen access to a Papal Indulgence, reducing the amount of time they would spend in Purgatory upon death.

Massacres ensued: a papal legate sent to France at the time made it clear that this was acceptable in Cathar-dominated cities. When asked how soldiers would distinguish between Cathars and other Christians, he purportedly said "Kill them all. God will know his own".

The Crusade lasted for several years. It didn't ultimately completely eradicate Catharism, but it did break the power of the secular lords who had supported it. In the end, the French crown, aligned with the Pope, held full power over southern France, in addition to their northern strongholds.