I know that they were victims of it, like with the Sack of Constantinople in 1204. But I'm wondering if the Orthodox had at any point in time participated in The Crusades, as in helping the Catholics fight the Muslim invaders. According to Wikipedia (which I understand is not necessarily the most accurate source of information), "The Crusades were originally launched in response to a call from the leaders of the Byzantine Empire for help to fight the expansion into Anatolia of Muslim Seljuk Turks", so I figure that at some point in time, the Orthodox were participants. Were they ever? I'm just curious.