By the 7th century BC, several Greek colonies were built on its Black Sea shore, and the earliest written Greek reports state that the lands were inhabited by Thracians, reidentified in time as Getae and then Dacians. During later times, the area also witnessed Celtic and Scythian invasions. It was part of the kingdom of Dacia for a period, after which the region was conquered by the Roman Empire, becoming part of the province of Moesia Inferior. With Diocletian's reforms, it was split from Moesia as a separate province of "Scythia", being part of the Diocese of Thrace. After the partition of the Empire in 395, the province was retained by the Byzantine Empire until it was annexed by the Bulgars following the Battle of Ongal.