History of Romania
The Dacians, who are widely accepted to be the same people as the Getae, with Roman sources predominantly using the name Dacian and Greek sources predominantly using the name Getae, were a branch of Thracians who inhabited Dacia, which corresponds with modern Romania, Moldova, northern Bulgaria, south-western Ukraine, Hungary east of the Danube river and West Banat in Serbia.
The earliest written evidence of people living in the territory of present-day Romania comes from Herodotus in Book IV of his Histories, which was written in c. 440 BCE; He writes that the tribal union/confederation of the Getae were defeated by the Persian Emperor Darius the Great during his campaign against the Scythians, and describes the Dacians as the bravest and most law-abiding of the Thracians.
The Dacians spoke a dialect of the Thracian language but were influenced culturally by the neighbouring Scythians in the east and by the Celtic invaders of Transylvania in the 4th century. Due to the fluctuating nature of the Dacian states, especially before the time of Burebista and before the 1st century AD, the Dacians would often be split into different kingdoms.
Geto-Dacians inhabited both sides of the Tisa river prior to the rise of the Celtic Boii and again after the latter were defeated by the Dacians under the king Burebista. It seems likely that the Dacian state arose as a tribal confederacy, which was united only by charismatic leadership in both military-political and ideological-religious domains. At the beginning of the 2nd century BCE (before 168 BCE), under the rule of king Rubobostes, a Dacian king in present-day Transylvania, the Dacians' power in the Carpathian basin increased after they defeated the Celts, who held power in the region since the Celtic invasion of Transylvania in the 4th century BCE.