Pope Innocent III

He ordered the recapture of Jerusalem from the Muslims in the Fourth Crusade. During this, the crusaders instead sacked Constantinople, establishing an alliance with the Byzantine
empire. While the crusades were terrible acts of violence perpetrated by Christians, it's important to learn about them to know the political,
sometimes violent past of the Church.
Behold, our inheritance has gone to strangers, our
houses to alien people.
•Pope Innocent III, Post miserabile