The style of warfare between the Greek city-states, which dates back until at least 650 BC (as dated by the 'Chigi vase'), was based around the hoplite phalanx supported by missile troops. The 'hoplites' were foot soldiers usually drawn from the members of the middle-classes (in Athens called the "zeugites"), who could afford the equipment necessary to fight in this manner. The heavy armour usually included a breastplate or a linothorax, greaves, a helmet, and a large round, concave shield (the "aspis or hoplon"). Hoplites were armed with long spears (the "dory"), which were significantly longer than Persian spears, and a sword (the "xiphos"). The heavy armour and longer spears made them superior in hand-to-hand combat and gave them significant protection against ranged attacks. Lightly armed skirmishers, the psiloi also comprised a part of Greek armies growing in importance during the conflict; at the Battle of Plataea, for instance, they may have formed over half the Greek army. Use of cavalry in Greek armies is not reported in the battles of the Greco-Persian Wars.