Simeon I of Bulgaria
In 925 Tomislav's Kingdom of Croatia emerged in the hinterland of the city, centered in Nin as an ally of Byzantium against Simeon I of Bulgaria - though without receiving any power from the Emperor over the Dalmatian cities. The rise of the rival Bishopric of Nin, headed by Bishop Gregory, which attempted to institute the "Slavonic" or "Slavic language" as the language of religious service, led to the 925 Synod of Split, at which it was decreed that "no one should presume to celebrate the divine mysteries in the Slavonic language, but only in Latin and Greek, and that no one of that tongue should be advanced to the holy orders".