Long before the Greeks crossed the Bosphorus and entered the Black Sea, the Thracians traded with other settlements on the Black Sea coast, as well as with the rich cities along the Mediterranean Sea, reaching even Egypt in the 12th-11th centuries BC.

The previous of Mesembria-Nessebar were clever people. Seafaring and fishing were very important to the city and they had to master the art of politics to protect the city from Persian, Celtic and Roman invasions. There are evidences that the rulers of Mesembria maintained friendly relations with the Celtic Kingdom of Cavar and also with the ruler of the Pontic Kingdom, Mithridates. Unlike the neighboring Apollonia, Mesembria was not subject to plunder by the Romans, because it voluntarily placed itself under their authority.