Ancient Greek warfare in the context of "Phalanx"

The Athenian military was the old main force of Athens, one of the major city-states (poleis) of Ancient Greece. It was largely similar to other armies of the region – see Ancient Greek warfare.

The Spartan army was the principal ground force of Sparta. It stood at the center of the ancient Greek city-state, consisting of citizens trained in the disciplines and honour of a warrior society. Subjected to military drills since early manhood, the Spartans became one of the most feared and formidable military forces in the Greek world, attaining legendary status in their wars against Persia. At the height of Sparta's power—between the 6th and 4th centuries BC—other Greeks commonly accepted that "one Spartan was worth several men of any other state."

Tradition states that the semi-mythical Spartan legislator Lycurgus first founded the iconic army. Referring to Sparta as having a "wall of men, instead of bricks," he proposed reforming the Spartan society to develop a military-focused lifestyle following "proper virtues" such as equality for the male citizens, austerity, strength, and fitness. Spartan boys deemed strong enough entered the agoge regime at the age of seven, undergoing intense and rigorous military training. Their education focused primarily on fostering cunningness, practicing sports and war tactics, and also included learning about poetry, music, academics, and sometimes politics. Those who passed the agoge by the age of 30 achieved full Spartan citizenship.

There is evidence of mercenaries (misthophoroi (plural), misthios (singular male), misthia (singular female) in Greek) being hired in Ancient Greece from the 6th century BC. The tyrants of that time hired bodyguards from other city-states. It is not known if earlier Aegean armies and navies, such as the Minoans and Mycenaeans, used mercenaries.

Mercenary troops from Caria and Ionia are known to have fought with Psamtik I against the Assyrians. These were the "bronze men from the sea" whose arrival in Egypt, according to Herodotus, was foretold to Psamtik by an oracle. They entered the country as raiders but Psamtik made a truce with 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 Ancient Greek armies, the psiloi (Ancient Greek ψιλοί, singular ψιλός, psilos, literally "bare, stripped") were light infantry who typically served as skirmishers and missile troops. They were distinguished from the armored hoplitai (heavy infantry) by their light weaponry and lack of armor.

In Classical Antiquity and Late Antiquity and throughout the existence of the Byzantine Empire, the lightest-armed troops, typically equipped with ranged weapons, and which fought irregularly in a loose formation, were deemed 'the psiloi'. Numbered among the psiloi were archers, the toxotai armed with a bow (toxa), and slingers, the (sphendonetai) who hurled stones or metal bullets with slings (sfendonai). Others, the akontistai, used the throwing javelin (akontia). Some psiloi simply threw stones at the enemy and were referred to as lithoboloi.