The Armies rule allows players to become more aggressive in the pursuit of conquest and plunder, since it allows them to create pieces that are specifically designed for warfare, rather than ones which primarily economic units.
The rule does require players to manufacture extra pieces for this purpose. I recommend producing four army tokens per player.
Army tokens are purchased during the Ship Construction phase, and are purchased from population or treasury tokens in the same manner as ships. Likewise, existing Army tokens must be supported in the same manner as ships.
When Army tokens are used, the Movement phase is divided up into 3 separate sub-phases, which are all carried out by each player before the next movement sub-phase:
During Conflict, Army tokens affect combat in the same manner as normal tokens. However, Army tokens are eligible for additional advantages.
Calculating "Combat Advantage" is important, since it is one of the chief things that Army units are good for. In Advanced Civilization, the only technology that provides "Combat Advantage" is Metalworking. When Army tokens are used, however, other sources of Advantage appear.
Combat Advantage Sources
Simply add up the total advantage for pieces in a space; if they include Army tokens, then include bonuses for Mathematics and Military. Otherwise, only count Metalworking for Advantage. Compare your Advantage Level to your opponent's, and whoever has the highest level subtracts his opponent's level to compute his net Advantage.
Once the level of Advantage is known, consult the table below for effects:
Though under this rule alone, Advantage can only go as high as 3, Advantage effects up to 5 are included in case other optional rules are used which affect Advantage.
Remember that regardless of what the chart says, once the total number of tokens in a space are equal to the population limit for that space, no more tokens need be removed. Armies do count towards population limits in a space. When tokens are being removed as a result of conflict, the owning player may select which tokens are removed first; if a player who had armies in a space removes all of them from conflict casualties, and the conflict is continuing, Advantage need not be recalculated.
When Reducing Surplus Population, Armies may be removed only if no more Population tokens exist in the space. However, Armies may exist in spaes that contain Cities (or a full complement of Town tokens); when this occurs, then Armies must be supported by Population in the same manner as Cities.
Likewise, during calamities, Army tokens count as Population tokens and may be removed from the board by their owner in the same manner.
During a Civil War, each space in which Army tokens and Population tokens (or Town tokens) coexist, one Population token is removed from the board for each Army token before factions are chosen. Army tokens have the same value as Population tokens when choosing factions. If, after Factions are chosen, an Army token coexists with an enemy City token, the City token is reduced.