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 them and hired them to his cause. Afterwards, he granted land to them alongside the Nile and they are traditionally held to have been the first Greeks to settle in Egypt. In the 5th century BC, Arcadian soldiers fought for Xerxes I in 480 when he led the Persian invasion of Greece. Later in the century, many Greek mercenaries were employed by Persian satraps, especially in Anatolia. During the Peloponnesian War, mercenaries from Thrace and other outlying regions were hired by both sides as hoplites and peltasts. In 401 BC, many Greeks supported Cyrus the Younger in his campaign against