Nice idea! In lieu of the upcoming Rome II Total War my suggestion would be...
Barbarian Badassesvisitors can't see pics , please
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loginAttackers: light armor and naked berserkers, light Kuyaks, two handed swords and axes, spears, light shields, some light cav and skirmishers, etc.
VSRoman Ruffiansvisitors can't see pics , please
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loginDefenders: medium armor, throwing weapons, heavy shields, one handed swords, archer squad, mounted general, etc.
Signups should be according to preference, class, and ability to use the available gear. I would suggest a forested area for the attack, resembling the Teutoburg Forest.
Another cool idea would be if the generals of the two armies (the actual attacker and defender Strat general) would need to be protected and there are extra points for killing them (counted in metagame).
We may be able to donate some troops from Derchios castle (1k or so) once I have confirmed this with our faction members.