Complex sentence: To prevent the Byzantine marriage, Fulk sent his envoy to Raymond of Poitiers in France to urge him to come to Antioch, which he did, traveling in disguise, because RogerII of Sicily wanted to capture him in southern Italy.
Split into simpler sentences: To prevent the Byzantine marriage, Fulk sent his envoy to Raymond of Poitiers to France to urge him to come to Antioch. He traveled in disguise, because Roger II of Sicily wanted to capture him in southern Italy.