Tomislav, from the Trpimirović dynasty, is considered to be the first king of Croatia. Nineteenth century historiography puts his coronation in the year 925, although many modern historians dispute this dating, putting even the event itself down to mere popular tradition. In the historical documents, Tomislav does not appear very frequently. He is first mentioned in writing by Thomas the Archdeacon of Split, as duke - dux croatorum – who was ruling in 914 (in his Historia Salonitana, Thomas writes “In the year of our Lord 914 at the time of Duke Tomislav…”) while he is called king (regi Crouatorum) in a letter of Pope John X of 925. He is also referred to as king in a note from the Church Council in Split in 925 (Tamisclao rege) and so this year has been accepted as the beginning of his reign.
Although little is known of his reign, it was in the time of Tomislav that the incursions of the Hungarians towards the Adriatic were stopped (Battle on the Drava, 917) and it is thought that it was under the rule of Tomislav that the Croatian state was expanded by the unification of coastal and inland parts (the coast and the Sava lowlands).He is ascribed a victory (Battle on the Drina, 925) over Emperor Simeon of Bulgaria who, having defeated the Serbs and taken Raška, then sent his Bulgarian army against the Croats. Constantine Porphyrogenitus, in his work De administrando imperio describes the Croatian army and navy of the time as large and strong, while the borders of the realm stretched from the Drava in the north, the Drina in the east, the Mirna and the Raša in the west to the sea in the south, an achievement that is also ascribed to Tomislav.
Robert Frangeš Mihanović, King Tomislav – relief, plaster, 1928-1938 (MZP-667)
It was not until the 19th century that F. Rački and I. Kukuljević Sakcinski wrote about Tomislav being the first Croatian king, who was crowned in 925 after victories over the Hungarians and Bulgarians. Giving a free interpretation of the Chronicle of the Priest of Dioclea, Kukuljević created a narrative of Tomislav being crowned in the plain of Duvno. Croatian historians of the time on the whole accepted this hypothesis, which was taken up whole-heartedly among the people, and in 1925 a big celebration of the 10th centennial of the Croatian kingdom was organised.