After reading wikipedia for about ten minutes, I hearby declare myself an expert on medieval history. Since the first crusade was called on by the Byzantine emperor, in a letter to the pope ,to reclaim Christian lands they lost to the Muslims(mainly the Turks)(The Turks REALLY wupped their butts), wouldn't it make sense for Orthodox factions to be able to join the crusades as well? I also read that Byzantine rulers were sending envoys to Song Dynasty China requesting aid against the Seljuks.(The Turks really wupped their butts)