A grand duke with complete control of the capital duchy (and the second duchy belonging to the same de jure kingdom as the capital duchy) is in a relatively strong position for greater ambitions. Beyond that, becoming a grand duke will give a +1 bonus to your demesne limit before modifiers. Thus, unless you have other factors in your favor, concentrate on expanding within your liege's realm, especially if you're a vassal count securing that first duchy title would help you greatly.Р”Р„s a vassal count, becoming the duke of the duchy your county belongs to is a step up in terms of military power. As a vassal, you get no bonus levies from your capital as a count, and a reduced bonus of +25% from the capital and +15% from the capital duchy if you're a duke or king. Independent rulers get a +50% bonus to levies from the capital, and +25% bonus from their capital duchy if they're a duke or above.

by only raising a county's worth of levies.Р”Р„s a vassal, your military is weaker than independent rulers of the same size and rank. This means that you technically can accept your liege's call to arms, but only contribute a bare minimum to the war effort, e.g. If you're tribal, you don't pay taxes to a tribal liege and you join your liege's war as an ally. If your feudal liege goes to war and raises your levies, you'll have to pay for them as well. Remember that as a vassal, you pay taxes to your feudal liege on a monthly basis.

13 Playing in an empire with viceroyalty law.

Crusader kings 2 how to play as duke