Battle of Gaugamela main Persian infantry was poorly trained and equipped in comparison to Alexander's pezhetairoi and hoplites. The only respectable infantry Darius had were his 2,000 Greek hoplites and his personal bodyguard, the 10,000 Immortals. The Greek mercenaries fought in a phalanx, armed not with a heavy shield but with spears no longer than three metres, while the spears of the Immortals were two metres long. Among the other Persian troops, the most heavily armed were the Armenians, who were armed the Greek way and probably fought as a phalanx. The rest of Darius' contingents were much more lightly armed; the main
Thracian warfare endured between the 5th century BC and the 3rd century BC. The Odrysian state was the first Thracian kingdom that acquired power in the region, by the unification of many Thracian tribes under a single ruler, King Teres 5th century BC. It became involved in wars and military conflicts against the Romans, Greek colonies, the kingdom of Macedon and the Diadochi, the Persian Empire, Paeonians, Dacians, Celts, Scythians and Thracian tribes. Sometimes it was allied with various Ancient Greek tribes or Greek city states. During the Peloponnesian war, Thracians were the allies of Athens. The Thracians fought alongside Athenians and