This article may contain outdated information that is inaccurate for the current version of the game. It was last updated for Vanilla.
A core is a province that is considered a rightful part of your state. Cores give several strategically important benefits:
- Provinces without a core add to your overextension (unless it's an overseas colony), proportional to their tax base value.
- Core provinces get a +75% positive tax modifier.
- Provinces with cores will have lesser chances for revolts.
- You always have a casus belli if one of your 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 land is not considered conquered or occupied but rather a rightful part of a realm.
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, it costs 20 AMP for provinces with an accepted culture, and 36 AMP for an unaccepted culture.
- An overseas province of your own culture (such as a colony) costs 10% of the normal cost to core. This is to encourage settling the New World and represents how colonies were not regarded as "conquered" or "taken", rather as claimed land.
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 national ideas reduce core-creation costs:
- Administrative: Adaptability
- Ottoman tradition:
- Russia: Sudebnik
- Timurid tradition:
- Italy: Path to Citizenship
- Ethiopia: Expansionist Policy
- Dai Viet: Don Dien
- Taungu: Bonus ideas
- Hordes: Tradition of Conquest
- Theocracies: Church Administration
- Anatolian Beyliks tradition:
- Maratha: Office of the Peshwa:
Enemy core creation
The following national ideas increase coring costs for a foreign power if they conquer provinces from a nation which possesses this modifier:
- Aristocracy: Local Nobility
- Bohemia: Czech Nationalism
- Dai Viet tradition:
- Brittany: Legacy of Breton Independence
- Berber tradition:
- Rajput tradition:
- Italian: Italian Aristocracy:
Other cost modifiers
- Having a claim on the province reduces cost by 25%.
- In the Holy Roman Empire the reform, Reform the Hofgericht, gives 10% reduced cost.
- The Policy "The Rapid-Integration Act"  gives 15% reduced cost.
- The Government Type Enlightened Despotism  gives a 5% reduced cost.
- War exhaustion: Every point of WE increases cost by +3%
- Overseas provinces of the national culture cost only 10% to core.
Coring is not instant. It takes 3 years, not counting any modifiers, to core a province. All the while you still have the overextension penalties to cost of stability and to your revolt risk.
When the province is occupied by rebels or a foreign power, the coring process is halted until the siege is lifted. Coring progress is also suspended when at war with a country which already has a core in the same province. Coring resumes after the war concludes.
Colonies that have grown into cities do not take as long to core as provinces seized from other countries.
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 you took it from a previous war and the province isn't in range.
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. (Note: the feeding strategy will cost Diplomatic Monarch Points after 1.6, and is arguably much less viable.)
- When negotiating a peace deal, a core can be removed:
- Through demanding to 'revoke 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.
- 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]
- 250 years if the core is the primary tag for the province's culture.
- 100 years if the core shares a culture group with the province.
- 50 years otherwise.
- The time is doubled if the core's owner does not exist.
- 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.