The separate Dacian tribes occupying most of modern Romania were unified under Burebista (60 - 44 BC) during which time Greek artisans were used in the building of the fortifications and hill forts and their rule was expanded south and west threatening Roman lands. Burebista's capital at Sarmizegetusa was high in the Carpathian Mountains of South Transylvania and was protected by a series of fortresses on the surrounding steep valley sides. After Burebista's death the the Dacian tribes fragmented again.
The Romans secured the Adriatic coast in BC 35 to BC 33, but the mountainous regions of Illyria were more difficult to penetrate. With the aim of securing a land route from Europe to the Middle East along the Danube and Romans took the Pannonian and Moesia. There is a Roman record stating that Gatae (from the modern southern Romania) were allowed to move to Moesia south of the Danube.