Divided into numerous tribes, the Thracians did not recognize themselves as a single group. Thrace and Thracians were names given them by the Greeks. The Thracians did not form a lasting political organization until the Odrysian state was founded in the 5th century B.C. The 4th century was a time of strife and Macedonian encroachment. The coins of the Thracian rulers, which were struck in the Greek cities of the kingdom, are so scarce that they may have been struck more symbolic of regal authority than to meet the needs of trade.