Tomislav, a descendant of Trpimir I, is considered one of the most prominent members of the Trpimirović dynasty. Sometime between 923 and 928, Tomislav succeeded in uniting the Croats of Pannonia and Dalmatia, each of which had been ruled separately by dukes. Although the exact geographical extent of Tomislav's kingdom is not fully known, Croatia probably covered most of Dalmatia, Pannonia, and northern and western Bosnia. Croatia at the time was administered as a group of eleven counties ("županije") and one banate (Banovina). Each of these regions had a fortified royal town.