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 Greek mercenaries me master and great king". Greek hoplites were widely admired for their skill as soldiers. The demand led many Greeks who faced poverty or exile to enlist as mercenaries in the pay of another state. Others, not so burdened with worry, became mercenaries through a desire for loot and adventure. In many Greek states, including Athens, the threats from Persia and Macedon required strong defensive forces. One of the main problems in creating and maintaining military strength was that peasant citizens could not afford to abandon their smallholdings for long periods of service and so the demand for professional soldiers