Complex sentence: After the Roman legions withdrew in 271 AD, it was overrun by a succession of various tribes, bringing it under the control of the Carpi (Dacian tribe), Visigoths, Huns, Gepids, Avars, Slavs and Bulgarians.
Split into simpler sentences: After the Roman legions withdrew in 271 AD, it was overrun by a succession of various tribes, which subjected it to various influences. During this time areas of it were under the control of the Carpi (Dacian tribe), Visigoths, Huns, Gepids, Avars, Slavs and Bulgarians.