an inscription found at Salona, appears to have been made by Tiberius. Southeast of the fortress, the traces of a Roman camp are still visible, as well as an inscription carved on a rock; both which are supposed to be contemporary with the siege under Tiberius. The description of this siege during the Illyrian Wars demonstrates that this place was strong and unreachable in those times. Migration period and the arrival of the Croats After the fall of the Roman Empire, Barbarians plundered the region around Klis. First it was ruled by Odoacer, and then by the Theodoric the Great, after he eliminated Odoacer, and set up an Ostrogothic Kingdom. After Justinian I fought an almost continual war for forty years to recover the old Roman Empire, he seized Dalmatia, and Klis was from 537, a part of Byzantine Empire. The name of Klis (Kleisa or Kleisoura) was first described in chapter 29 of Emperor Constantine Porphyrogenitus' De Administrando Imperio. While describing the Roman settlement of Salona, Constantine VII speaks of the stronghold, which may have been designed or improved, to prevent attacks on the coastal cities and roads by Slavs. Salona, the capital of the province of Dalmatia was sacked and destroyed in 614 by Avars and Slavs. The population fled to Diocletian's walled palace of Split, which was able to resist the invaders. Thereafter, Split rose quickly in importance as one of Dalmatia's major cities. In the 7th Century the Avars were driven out by a second wave of Croats., on the invitation by the Emperor Heraclius in order to counter the Avar threat to the Byzantine Empire. Royal Castle From the early 7th century on, Klis was an important Croat stronghold, and later, one of the seats of many Croatia's rulers. In the 9th century, Croatian duke Mislav of the Duchy of Croatia, from 835 to 845, made the castle of Klis seat of his throne. Despite Frankish overlordship, the Franks had almost no role in Croatia in the period from the 820s through 840s. After Mislav's death, starting with Duke Trpimir I, Klis was ruled by royal members of the House of Trpimirović, who were at first Dukes of the Croatian Duchy (dux Croatorum), and afterwards Kings of the Croatian Kingdom (rex Croatorum). They developed the early Roman stronghold into their capital. Relations with the Byzantines greatly improved under the Croatian duke Trpimir I, who moved