Celts
After his death in 281 BCE, Celtic tribes from the Adriatic coast region and possibly from much further afield, invaded Thrace and Greece. A detachment, consisting of the Tectosages, the Tolistoagii (Tolistobogii) and the Trocmi, was invited into Asia Minor by the Bithynian king Nicomedes I. There the Celts settled in Galatia the region called after them.

Bastarnae
Towards the end of the 3rd century the Thracian land north of the Danube was invaded and settled by the Bastarnae, a German tribe that remained a powerful force until subdued by M. Licinius Crassus in 29 BCE. In 279 CE the Emperor Probus settled the Bastarnae south of the river to protect the frontier from other Germanic peoples trying to expand to the south.