In War Kingdoms, when two armies battle against each other, the total attack value of the aggressor is compared to that of its opponent. The army with the higher total attack value becomes victorious. While in a war of conquest, this rule is the only determiner of the ultimate result of the battle, the outcome is affected by certain other factors such as the strength of the city wall in a war of plundering.

Total attack value of an army is the sum of the damages given by each unit. Each unit has an infantry, cavalry and ranged attack power. The damage given to a unit is the respective attack power of the other unit. For example, if unit X (infantry) and unit Y (cavalry) fight against each other, the damage taken by unit X is equal to the infantry attack power of unit Y and the damage taken by unit Y is equal to the cavalry attack power of unit X. The unit who takes less damage wins the fight.

All military units are classified into 3 subgroups; infantry, cavalry and ranged. Units have different characteristics based on their infantry, cavalry and ranged attack powers. For this reason, a particular unit that is strong against infantry units can be weak against cavalry units.

Players can not be attacked during their beginners protection. This begins when they have registered and lasts for up to 72 hours. Protection Mode can be inactivated by attacking to another kingdom.