A capital is a ruler's primary county.
The location of the capital determines:
- where the court is located
- where mercenaries and Holy Orders will spawn. The range of mercenary companies available depends on the distance between the capital and the companies' headquarters.
- the levels shown in the technology screen. All technological investments made will slowly diffuse from there to the rest of the realm
- the cultural bonuses that are applied to the whole realm (relations, legalism, ...), which depend only on the capital's technological level.
- When investing in new tech, the levels shown are for your capital and all investments made will slowly diffuse from there to the rest of the area.
- it is worth more warscore once occupied than other provinces during wars.
- Vassals far from your capital are more likely to seek independence (and vassals bordering the capital duchy cannot create an independence faction)
- the de jure structure taken into account to calculate levies modifiers, since patch 2.0.
Changing the capital
A capital can be changed:
- once per a ruler's lifetime to any other county within the ruler's demesne (using the button in the top left of the county screen).
- any time when moving the capital to the historical location for the primary title (can be seen in the province description on the de jure maps). AI rulers will most often do it.
- by granting the current capital county to a vassal. The new capital county will be the one at the top of the list of lands that can be granted, and is typically the oldest held county.
Select provinces with 4/5/6 holdings: choosing provinces with more available holding slots allow to construct more and increase the number of direct baron vassals, and thus taxation. In gavelkind succession, the capital province is maybe the only province that will be inherited for certain.
Select most technologically advanced provinces for short term bonuses and spread of technology.
Place the capital at the centre of the realm, to minimize distance penalties.
With multiple same-rank titles, choose the county with the largest de jure structure: to maximise levies modifiers, place your capital in the biggest county of the biggest duchy of the biggest kingdom of the biggest empire.