Perhaps one of the odder units of the Celtic factions, the Gaesatae consist of roving warriors who fought naked in the field. Gaesatae are light skirmisher units which can be recruited by the Arverni from the Meeting House, and because of the amount of experience and confidence that they have, they are extremely lethal skirmisher units — the fact that they appear stark naked on the battlefield is meant to show that they are expert fighters who do not need armour.
Nakedness need not always be a dearth of power: for one thing, their lack of armour or clothing makes them unusually fast on foot, which when coupled with their large shields and prowess in combat, make them exceedingly deadly. Use their speed on foot and the vast reach of their weapons to counter enemy melee units, especially light cavalry but be wary of getting them caught in fights with heavy infantry or ranged units. Cheap levy units such as Rorarii or Spear Levies can be used to distract the Gaesatae, who then can be attacked, preferably from the flank using cavalry archers or foot archers, whose weapons will outrange the javelins thrown by them. Against fortifications, however, Gaesatae are mostly worthless.
Gaesatae were Celtic warriors who hailed from the lands surrounding the north and western Alps in the early pre-Imperial days of the Roman republic.They made notable appearances in Roman history fighting with the Italo-Celtic tribes of the north, as well as auxiliary units with the Carthaginians under Hamilcar Barca during the Second Punic Wars.
According to the Greek historian Polybius, they were noted for fighting naked, wearing no clothes or armour whatsoever, except for a shield and their weapons and occassionally some jewellery and possibly a helmet. Stripping down for combat was meant to demonstrate their combat prowess, staunch faith in their gods and their skills, as well as to intimidate other opponents — although Polybius also mentions that the gaesatae may have done so because they did not want to get impeded in movement by their own clothes.
The name "gaesatae" is a bit of a mystery: Polybius says that the name itself meant "spearmen" but modern Celtic linguists argue that it probably meant something closer to "bounded men" or "bondsmen", the words gaison (spear) and geas- (prohibition or limit) being close enough to confuse outsiders not acquainted with the Celtic languages. If so, then these warriors could fit the description of mercenaries, being bonded together by comradeship in arms beyond the bonds of traditional tribal society which fits in with Polybius' comments that the gaesatae fought as mercenaries.