Complex sentence: Once exiled, Vuk attempted to gain outside help against Tvrtko; he particularly pleaded with Pope Urban V, as the Papacy had been advocating a crusade against the Bosnian Church for some time.
Split into simpler sentences: Once exiled, Vuk attempted to gain help against Tvrtko from the outside. He particularly pleaded with Pope Urban V, as the Papacy had been advocating a crusade against the Bosnian Church for some time.