Province of the Roman Empire in the lower Danube area, extending from Serbia to the mouth of the Danube and between Dacia and Thracia. Moesia was conquered by Marcus Licinius Crassus in 30-28 BC and became a Roman province in 15 AD. In the 1st century AD, a series of defensive walls and forts in southern Romania were built to guard the Moesia-Dacia frontier. Moesia was fairly prosperous because of the wheat from the Black Sea area. Agriculture and fruit-growing flourished, and there was mineral wealth in the Balkan Mountains. The province suffered heavily from barbarian invasions in the 3rd century AD, and when Dacia was abandoned about 270, its inhabitants were largely transferred to Moesia. Moesia remained part of the Eastern Roman Empire until the 7th century.