Types of Combat Units
With a few exceptions, all combat units belong to one of these types:
- Infantry: Warriors fighting on foot, with swords, bows and arrows, etc.,
- Cavalry: Warriors on horseback,
- Siege weapons, such as catapults, and
- War ships, such as triremes.
Melee vs. Ranged Units
Some of the units mentioned here are melee units, which can only fight when very close to the enemy (e.g., with a sword); Others are ranged units, which shoot or throw a weapon from afar, so they only need to get close enough to be within range (but not too close). Each of these types has its advantages and disadvantages. For example, some ranged units may be very powerful against certain melee units from a distance, but helplessly vulnerable to melee attack from up close.
Types of Damage and Balancing
Damage in 0 A.D. comes in three types: hack, pierce and crush. Units have different armor for each type. In addition, unit attacks may be of multiple types simultaneously, e.g., a hoplite does both pierce and hack damage.
On top of this, some units have special bonuses against particular other units, e.g., spearmen defeat melee cavalry, but are countered by skirmishers and cavalry archers.
Consider that different units have different movement speeds, firing rates, hit points and costs, and you get a complex game with many strategic choices to make when choosing how to spend your resources. In-game documentation can be found in each unit’s description when hovering above the button to train it.