The Odrysian Kingdom was a union of Thracian tribes under the kings of the powerful Odrysian tribe centered around the region of Thrace. Various parts of Thrace were under Macedonian rule under Philip II of Macedon, Alexander the Great, Lysimachus, Ptolemy II, and Philip V but were also often ruled by their own kings. The Thracians and Agrianes were widely used by Alexander as peltasts and light cavalry, forming about one fifth of his army. The Diadochi also used Thracian mercenaries in their armies and they were also used as colonists. The Odrysians used Greek as the language of administration and of the nobility. The nobility also adopted Greek fashions in dress, ornament and military equipment, spreading it to the other tribes. Thracian kings were among the first to be Hellenized.