sentences:  Croatian Kingdom as an ally of Byzantine Empire was in conflict with the rising Bulgarian Empire ruled by Tsar Simeon I.In 923, due to a deal of Pope John X and a Patriarch of Constantinopole, the sovereignty of Byzantine coastal cities in Dalmatia came under Tomislav's Governancy.The war escalated on 27 May 927, in the battle of the Bosnian Highlands, after Serbs were conquered and some fled to the Croatian Kingdom.