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
Regions of ancient Greece () was an ancient Greek region in Epirus. "Macedonia" or "Macedon" (from , "") was an ancient Greek kingdom and region, centered in the northeastern part of the Greek peninsula, bordered by Epirus to the west, Paionia to the north, Thrace to the east and Thessaly to the south. Early geographers put river Strimon as the eastern border of Macedonia with Thrace. However, as kingdom of Macedon was expanding and was pushing east the Thracian tribes, river Nestos was regarded as the eastern border of the region and Sintice, Odomantis and Edonis were included in it. Traditionally part of Thrace