This article is considered accurate for the current version of the game.
A core is a province that is considered a rightful part of a country. Cores give several strategically important benefits:
- Provinces without a core add to overextension (except colonies), proportional to their tax base value.
- Core provinces get a +75% positive tax modifier.
- A country will always have a casus belli if one of their core provinces is owned by another power.
Coring is the act of adopting a province into what is considered one's patrimony, or rightful homeland. Cored provinces are not considered conquered or occupied, but rather a rightful part of a realm.
- Usually coring range is the same as colonial range. The following ideas and policies increase colonial range:
- If a country has a core in province A, then it can core any province that has a "land bridge" to A. A doesn't have to be owned by that country.
- If a country's vassal has a core in province B, then the country can core any province adjacent to B in its home continent. B doesn't have to be be owned by that vassal.
- If a country's colonial nation has a core in province C, then the country can core any province adjacent to C in all continents. B doesn't have to be be owned by that colonial nation
Coring is an action which costs administrative monarch points. The amount of points needed and therefore time it takes to core a province depends on:
- Base cost depends on base tax: for each 1 base tax, the cost is 20 AMP. (In older patches, provinces with unaccepted cultures cost more; this is no longer the case).
- An overseas province costs 50% of the normal cost to core.
- War exhaustion increases coring cost by 2.5% per point.
- Same-continent colonies, or those with a land connection to the capital, cost 50% of the normal cost. Overseas colonies are automatically cored for free when they become a city.
Coring costs do not depend on:
- Your current overextension.
- The distance from your current cores.
- Your current stability.
- If you are at war or not.
Reducing core costs
The following ideas and policies reduce core-creation costs:
Costs are also reduced by:
- A claim on the province reduces cost by 25%.
- The third HRE reform, Reform the Hofgericht, gives 10% reduced cost for the emperor.
- The Government Type Enlightened Despotism  gives a 5% reduced cost.
- Hindu who chose Shiva as the current rulers' diety recieve 10% reduced cost.
The national ideas listed below increase coring costs for a foreign power if they conquer provinces from a nation which possesses this modifier. The increase applies even if the nation with the core does not exist. These modifiers are taken into account by the AI when making decisions on which nation to attack.
The base duration for coring is 3 years, and it can be reduced by the following modifiers:
- Province has same culture group: -50%
- Province is claimed: -10%
The two modifiers above will stack multiplicatively. Coring progress will be halted if the province is occupied hostile forces or when the current owner is at war with any country that already has a core on the province. Progress will resume as soon as these conditions are lifted.
It is not possible to core a province
- while being at war with someone who also has a core in that province. The ongoing core creation will temporarily halt if this happens.
- while there is a missionary converting the province
- while the culture of the province is being changed
- if the province isn't in range.
- Province is occupied (All progress lost)
- Province is under siege (Progress halts, will resume if siege is lifted)
Gaining cores through other means
In addition to coring newly acquired provinces manually, a nation can also gain cores by diplo-annexation of vassals or integrating a junior partner of a personal union. Both processes automatically give cores on all provinces of the acquired territory, making the strategy of "feeding" vassals with uncored provinces a viable strategy to save monarch points. However, provinces cored this way begin with high local autonomy and will be relatively unproductive for some time, depending on your government type.
When an overseas colony (not on the same continent as the player's capital) becomes a city, its owner gains a free core on it. Colonies on the same continent don't receive free cores, but have reduced coring cost. If the owner has a Colonial nation in the same colonial region (or becomes eligible for one with the colony finished), the core is instantly granted to the colonial nation instead.
- When negotiating a peace deal, a core can be removed:
- Through demanding to 'revoke core'. You can't make a nation revoke a core on land you do not have as a core.
- If you force a nation to 'return core's to a third nation, the nation giving away the province loses the core if the province is not of their primary culture.
- Cores in uncontrolled provinces will disappear some time after the most recent of these events:
- The province changed ownership.[Does not work]
- A war between the current owner and the nation owning the core was fought.
- The owner of the core lost ownership of the province.
- The time to lose a core depends on the province's culture relative to the core:[Needs verification]
- If the core is the primary tag for the province's culture, it cannot expire.
- 150 years if the core shares a culture group with the province.
- 50 years otherwise.
- If a country is destroyed, it loses all wrong-culture group cores.
- Releasing nations will remove cores from releaser if the province is not of their primary culture.
- Cores can also be removed on provinces that you don't own by going to the province view and removing the core manually. However, this action also costs some prestige.