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
Heavy infantry Heavy infantry Heavy infantry refers to heavily armed and armoured infantrymen trained to mount frontal assaults and/or anchor the defensive center of a battle line. This differentiates them from light infantry which are relatively mobile and lightly armoured skirmisher troops intended for screening, scouting, and other roles unsuited to the heavier soldiers. Heavy infantry typically make use of dense battlefield formations, such as shield wall or phalanx, multiplying their effective weight of arms with weight of numbers. Heavy infantry were critical to many ancient armies, such as the Greek hoplites, Macedonian phalangites, and Roman legionaries. After the fall of Rome,