Units in 0 A.D. can be placed on a continuum from “civilian-only”, which are almost exclusively used for accumulating resources, to “military-only”, which can only fight. In the middle, the game features a wide variety of citizen soldiers, which can do a little bit of both.
You usually start out a game with a few female citizens, who are the driving force of your economy. They specialize in gathering resources, particularly Food, by foraging and farming more efficiently than other units. They can also build civic buildings, such as resource dropsites, and cause nearby male units to work faster. Although they can attack enemy units, they are very vulnerable to practically any other unit.
Some units have the dual role of both workers and soldiers, meaning they are citizen soldiers. For example, hoplites can not only fight but also chop wood. Citizen Soldiers have bonuses for gathering wood, stone and metal. Certain buildings, such as fortresses, can only be built by citizen soldiers.
The more citizen soldiers fight, the more battle experience they gain, and automatically go up the ranks. With each rank, they become stronger, and don a unique appearance, but also get gradually worse at “civilian” tasks, such as gathering resources.
Champions and Heroes
You may also train champion units, which are more expensive than citizen soldiers and cannot do any task but fight, but are stronger and better at fighting. You can also train exactly one hero in a game, which is a very strong unique unit.