It is calculated by adding the levies of all buildings in a holding to the base levies of that holding. This is quite similar to holding income, except with soldiers instead of gold. These three factors are multiplied together to decide how many levies you can raise. How many levies you can raise depend on three factors: General info on Crusader Kings II troop types : Levy (from Game Mechanics category) I'll therefore be going into how levies work, and what you can do to get more. As levies are core to your ability to defend yourself, understanding how to get as many as possible is important. At the time few had anything resembling standing armies, instead drafting peasants in times of war. In Crusader Kings II, most of your military is based around levies.
