Warfare occurred throughout the history of Ancient Greece, from the Greek Dark Ages onward. The Greek 'Dark Ages' drew to an end as a significant increase in population allowed urbanized culture to be restored, which led to the rise of the city-states (Poleis). These developments ushered in the period of Archaic Greece. They also restored the capability of organized warfare between these Poleis. The fractious nature of Ancient Greek society seems to have made continuous conflict on this larger scale inevitable.

The phalanx was a rectangular mass military formation, usually composed entirely of heavy infantry armed with spears, pikes, sarissas, or similar polearms tightly packed together. The term is particularly used to describe the use of this formation in ancient Greek warfare, although the ancient Greek writers used it to also describe any massed infantry formation, regardless of its equipment. Arrian uses the term in his Array against the Alans when he refers to his legions. In Greek texts, the phalanx may be deployed for battle, on the march, or even camped, thus describing the mass of infantry or cavalry that would deploy in line during battle. They marched forward as one entity.