A rebellion is a general revolt by disaffected inhabitants of a province, seeking independence from what they see as an oppressive and unjust overlord. Rebellions generally occur as a result of significant unhappiness in the pops of a province, which generate unrest and decrease provincial loyalty until tensions reach a boiling point and the province revolts. Individual rebellions of isolated provinces are rarely dangerous and can usually be easily suppressed, but widespread discontent can lead to a large wave of revolts that can seriously tax the military resources of a country or a complete collapse of its authority.
Unrest represents the overall degree of discontent in a territory, and is generated by unhappy pops (those with a happiness below 50). The happiness of a pop depends on its culture and its religion, as compared to the country’s state religion and culture. Different pop-types also want different civilization levels to be happy: while tribesmen want it as low as possible, citizens want it at a rather high level. Different laws make different pop types more or less happy as well. Access to different goods in the city will also make pops happier. The amount of unrest a pop produces differs based on its political weight, which is determined by its class; unhappy nobles are much more problematic than discontent slaves.
Every pop with less than 50% happiness will contribute to the unrest of the territory according to the following formula:
Each point of unrest gives the following modifiers:
- -0.08 Territory Provincial Loyalty
- −10% Pop Promotion Speed
- +10% Pop Demotion Speed
- −1 Migration Attraction
- +25% Pop Migration Speed
The Territory Provincial Loyalty modifier is scaled according to the relative population size of the territory (compared to the population of the province as a whole) before being applied to the overall loyalty of the province. Notably, unrest does not directly decrease a territory's output, though the output will usually be reduced anyways by the unhappy pops the generated the unrest in the first place.
An army without a general can be assigned to a regional governor. Once assigned, the army cannot leave the region until detached again, but it can freely move within the region. It can even fight in a war and occupy enemy land inside the geographical region, with governor simultaneously acting as an unpaid general for all his armies. Unlike with generals, there is no cooldown on assigning and detaching an army to a region.
Each full cohort of the assigned army suppresses -1 unrest in each city per 25 province pops (see game file references to AREA_TROOPS_POP_COUNT). Suppression is capped at -4 unrest.
Cohorts lacking manpower count proportionally.
Neither cohort's morale (maintenance), nor governor's attributes impact the suppression.
Since provinces in the same region will usually have different population densities, unrest suppression in each province will also be different. For example, a 4-cohort army assigned to a region with a 25-pop province and a 100-pop province will suppress 4 unrest in every city of the first province and 1 unrest in every city of the second province.
- Main article: Province loyalty
Each province has a provincial loyalty value representing how willing it is to accept its owner's rule and obey orders from the capital. A province is considered disloyal if its loyalty goes below 33, at which point most interactions with the province will become unavailable:
- Regiments recruitment
- Building construction
- Manual pop movement
Province loyalty is primarily decreased by unrest in its territories, weighted according to their population, as well as governor corruption. Besides addressing the main sources of discontent, province loyalty can be increased by appointing a more loyal governor and using the Harsh Treatement governor policy. Monarchs may also use the Anabasis action while in command of an army at a provincial capital to increase province loyalty.
A province's loyalty reaching 0 is the main trigger for a rebellion.
A rebellion will occur when the loyalty of a unoccupied province reaches 0. When that happens, the province will declare independence, either creating a new country with the name of the province or reviving a previously existing country in the area that was annexed. The rebelling nation will then either declare war with its former owner using the Independence wargoal for its province, which requires the revolt to retain control of its entire province in order to gain ticking warscore (the defending former owner must instead control at least one of the rebellion's territory to gain ticking warscore), or join an existing war of independence if another province of the same culture is already in revolt. For player-controlled nations, this can lead to a growing cascade of rebelling provinces if there is widespread discontent and falling provincial loyalty across the board, though AI-controlled countries get a boost of +35 province loyalty when a rebellion occurs that will generally prevent them from falling apart too quickly.