While a major revolt is not very different from having a large nation revolt in other Paradox games, civil wars are dramatically different. A particularly weak or tyrannical ruler can see a significant portion of their characters, armies, and provinces revolt against in them in the name of overthrowing the government.
The countdown to a civil war will begin when the power base of all disloyal characters as a share of the country's total power base is greater than the state's current Civil War Threshold. The base threshold is 25%, which is decreased by tyranny and higher country rank. Larger nations therefore tend to be more prone to civil wars, as they have more powerful characters to handle and need a smaller proportion of them to be disloyal before a civil war can break out. This timer ticks up every month, and if the situation is not brought under control, the civil war will break out after 40 months. During this time, there will be an alert notifying the player that attention should be given to the loyalty of powerful characters immediately. Of course, there are also alerts as soon as a single province or a general is disloyal.
It is also possible for civil wars to be triggered outside of the usual civil war counter, most notably as one of the possible outcomes when failing to successfully convict when bringing a powerful character to trial. There are also a number of unique mission and event chains that can trigger civil wars , such as with the invasion of Magos in the Cyrenaican Opposition, the overthrow of the 20px Syracusan Tyranny, and in some of the Roman flavor events.
A character's loyalty to the government is one of their most critical aspects and is important to keep in mind when allocating positions and making decisions that affect the loyalty of characters, particularly of those with a large power base. When the loyalty of a character drops below 33, that character is considered disloyal and will begin to actively go against the government, stirring up discontent in other characters, refusing to abandon their positions, armies, or governorships, and generally ignoring any orders from above. If enough powerful characters are disloyal, they will form a bloc to launch a civil war.
Power base is one of the largest factors affecting character loyalty, with powerful characters - especially heads of family - being both the hardest to keep pleased yet the most dangerous if they become disloyal. Characters of scorned families also have a significant loyalty malus, while high will significantly decrease loyalty across all characters. Monarchies must in particular contend with pretenders, particularly if they have a large amount of support, while in republics members of factions with low approval will also have a significant malus. Certain actions such as revoking positions and holdings will also anger characters, if temporarily. However, there are also a large number of ways to increase a character's loyalty temporarily or permanently, such as by making friends, granting a position or holding, giving bribes and free hands, and more. A large variety of event options can also temporarily affect loyalty either way. Over the course of the game cumulative general loyalty bonuses from inventions, laws, national ideas, and other permanent modifiers will generally tend to increase loyalty overall.
Generally, it is most important to ensure the loyalty of powerful characters by any means possible, whether by plying them with flattery and bribes or choosing event options to keep them content even at the expense of something or someone else. At the same time, power base should generally be divided up such that no character becomes too powerful and becomes impossible to keep loyal, which for instance means being wary of granting too large and army or governorship to a character that already has a large power base (especially heads of family) or splitting up armies that take up too much of the country's total military, so that its general is not too powerful.
When commanded by a general, every cohort in an army has a monthly chance to become loyal to their commander, based on the Cohort Loyalty Gain Chance modifiers of the general, the army, the country. The total chance of cohort loyalty is a base of +0.50% per month and is increased by the general's charisma, popularity, and wealth, as well as when drilling the army, but is reduced to 10% of its normal value when not in battle. Cohort loyalty can also be gained when sacking cities in a war.
When a cohort is loyal to a character, the country pays only 66% of its normal maintenance for it, as the character it is loyal to will pay the unit him or herself.
Loyal cohorts always provide power base to the character they are loyal to and will join their sponsor's side in any civil wars, rather than following their commander - even if the two are different. This applies even if the character they are loyal to is no longer a general at all, and this means that a particularly long-lasting and/or successful general that has gained the loyalty of many of their cohorts will continue to keep the power base associated with those cohorts even if dismissed, which can be a problem if the general has become powerful or disloyal. Disbanding a loyal cohort will not remove this power base; instead, the character will gain loyal veterans that continue to provide power base even though they are no longer part of the army, and can be raised again if their sponsor rebels as part of a civil war.
When the civil war begins, a new dynamic tag is created with all disloyal characters as well as their friends and immediate family members joining the revolt, bringing along all held governorships and holdings as well as commanded armies and loyal cohorts and veterans. Disloyal subjects may also side with the civil war revolter, who will additionally start new wars with any nation that the parent country was already at war with. Civil war tags can be recognized by their name, which will always be the adjective of their parent nation followed by "Revolt". The flag will normally be randomly generated, but a few major states have pre-scripted flags for their civil war revolters that reflect an inversion of their normal flags:
Additionally, certain event/mission-triggered civil wars will also have a unique rebellion name.
A civil war is a war-to-the-death, where territories automatically switch owners when they are occupied, and losing a civil war is considered a game over like any other annexation. Peace deals cannot be made during civil wars; the only way to end them is to completely destroy the other side, typically by destroying or decisively defeating all of their armies. Generally, unless the country is very small civil wars are a large drain on time and resources and should generally be avoided at all costs; equally, a period of civil war is a great time to strike at a now-weakened rival or even a significantly larger power that under normal circumstances would be far too strong to take on.
- Consolidate the capital region first: Since the capital region is less prone to rebellion compared to other regions, fully occupying the region helps the ruler with their power base. Conversely, expanding in other regions empowers the regional governor first, before the ruler.
- Track the holdings held by family heads: A crucial source of power base for family heads is their holdings, especially if their holdings have many pops. Consider rewarding the family head with a holding with few pops after revoking one with many.
The following thread in Paradox Forum discusses more strategies suggested by players to deal with characters loyalty leading to civil war: