Complex sentence: Manuel only forgave him after Raynald agreed to accept a Greek Patriarch in Antioch, also promising that he would allow a Byzantine garrison to stay in the citadel of his capital whenever it was required and send a troop to fight in the Byzantine army.
Split into simpler sentences: Manuel only forgave him after Raynald agreed to accept a Greek Patriarch in Antioch. Raynald also had to promise that he would allow a Byzantine garrison to stay in the citadel whenever it was required and would send a troop to fight in the Byzantine army.