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
Ancient Macedonian army almost invariably part of any force on detached duty, especially missions requiring speed of movement. Other nationalities also provided peltasts for the Macedonian army. Especially numerous were the Thracians; the Thracian peltasts performed the same function in battle as the Agrianians, but for the left wing of the army. It is unclear if the Thracians, Paeonians, and Illyrians fighting as javelin throwers, slingers, and archers serving in Macedonian armies from the reign of Philip II onward were conscripted as allies via a treaty or were simply hired mercenaries. Peltasts were armed with a number of javelins and a sword, carried