Jean X
Tomislav attended the Church Council of Split in 925, convened by Pope John X to discuss the use of Slavic language in liturgy and the ecclesiastical jurisdiction over Croatia and the Byzantine Theme of Dalmatia. Although the Pope sought to prohibit Slavic liturgy, the Council did not agree, while jurisdiction was given to the archbishop of Split instead of Bishop Gregory of Nin. Since the historical sources about Tomislav are scarce, the exact year of his accession and his death are not known. The rule of his successors was marked by a series of civil wars in Croatia and a gradual weakening of the country.