Civil War (out of date)

This guide is out of date but I have had a recent contribution and anyone else who wants to add in will be credited as well.

"Hello Voth. Can you please add the other, simplified way, to prevent civil war? By reducing your power (depending on your faction) to below 50% (for Romans) and for hellenic factions around 50-60%. It's a lot easier then constantly trying to assassinate your generals, adopting them or using military alliances to have more territory but not cause civil war. Thanks" Pony Slaystation 3

The Civil War game mechanic is enabled at level 2 emperium. Level 2 imperium is the tier when you can recruit 9 armies. Before this point approval raitings only matter if you want to put off the Civil War as long as possible.

The Imperium tracker in the faction menu measures your Imperium by your land holdings, each new settlement you take, not province, drives the Imperium up one increment. Understanding this alllows you to easily time spawning a Civil War as you manipulate the approval ratings.

Civil war is forced to start at max level Imperium, a simple mouse over of the Imperium tracker will tell you "civil war is brewing".

There are two types of Civil Wars, Approval Wars and Ambition Wars. There are three factors that effect these two types of war.

Approval Rating is the trigger for Approval War. In republics approvals below 15% and above 75% can cause a Civil War. In Kingdoms approvals below 50% can cause a Civil War.

Gravitas effects your Approval Rating by slowly causing it to increase or decrease over time based off your sub faction's Gravitas vs that of the opposing sub factions. It also plays a roll in the effects of Ambition.

Ambition is the trigger for Ambition War. Ambition functions as a multiplier to Gravitas. A character with 3 Ambition becomes a threat at approximately 35 Gravitas, 2 Ambition character at 50, 1 Ambition at 100. Members of your own sub action can cause an Ambition War to spawn as well, though their threshold for threat seems to be higher.

Approval Wars are simple to trigger or prevent and represent your sub faction as a whole being viewed at too weak or too strong by the opposing sub factions.

Ambition Wars are harder to trigger and prevent and represent a member of a sub faction becoming a Julius Caesar type figure.

All Civil War spawns seem to be based off of a percentile, especially in Ambition Wars. The threat individuals pose manifest in an X% chance they will trigger a Civil War each turn. Loading an auto save at very hard and lower dificulty will sometimes undo the Civil War, giving you time to find and eliminate the trigger.

Political Actions serve as a means to maintain the balance required to minimize the chances of a Civil War. Well planned Political Actions can be used to create the balance required for your government type and keep control over dangerous characters with high Ambition. Political Actions reduce your Approval Rating by a few points at first, so spamming them is generally a bad idea.

Kingdoms
Marriage: Don't marry, ever. If your approval rating is low enough to benifit from marriage you are doing it wrong.
Adopt: This is an easy way to control approval. Target the high Ambition characters first.
Bribe: The expensive adoption.
Secure Promotion: After winning a battle, this will increase Gravitas.
Assassinate: This is for dealing with problem characters, those with high Ambition or the sub faction leader.

Republics
Marriage: This functions as a sort of tether to the other houses, to a certain degree, equalizing your Approval Rating. If you Approval is higher than the house married into, it will be lowered, conversely, if your Approval is lower, it will be raised.
Adopt: This can be a cheap way to deal with a high Ambition character.
Bribe: The expensive way to deal with a high Ambition character.
Secure Promotion: After winning a battle, this will increase Gravitas.
Assassinate: This is for dealing with problem characters, those with high Ambition or sub faction leaders with high Gravitas.

It should be noted that leaders of the other house/sub factions cannot be adopted or bribed.

In Approval Wars armies and fleets always spawn at your faction capital. You can easily know what your captital is by checking your faction menu.

In Ambition Wars the armies and fleets spawn in a low public order settlement close to the threatening character. This usually happens at a newly captured settlement as they have poor public order and the fighting general just received Gravitas.

Thanks to Lustrati and Puddingkip for their contributions in determining location.

There are two ways to end a Civil War, by quelling the rebellion or signing a peace treaty.

• Quelling: You destroy all armies and navies contolled by the usurpers. I had one case early on where the Civil War ended with the destruction of 9 of 12 enemy armies, this may be due to an Ambition war and the killing of the offending general.
  
• Peace: Paraphrasing from the in game encyclopedia, after a certain time a peace treaty will be automatically negotiated, the terms of which are based on the balance of power at the end of the war.

I have no experience with the peace treaty or possible duration of a Civil War upon signing. If anyone does, input is appreciated and props given.

Quelling a Civil War has a different outcome based on the government of your faction.

~Kingdoms: After Quelling a Civil War there is no change to the government, you are still the supreme leader.

~Republics: After Quelling a Civil War you are prompted on the next turn to either continue as a Republic or become an Empire.

• Republic: +2 recruitment slots and -10% on unit training costs across all provinces.
  
• Empire: -10% unit upkeep and -25% corruption.

After a Quell the political system ceases to function, it can be ignored as a Civil War will never spawn again.

Peace is an outcome I have never reached. In theory, depending on the balance of power, the Empire option would be impossible. Also it seems possible the political system could still function. If anyone has eperience with this please share.

~Rebel armies spawn with your tech level.
~Kill any 2-3 Ambition characters you cannot control.
~Marriage is the only political action that can raise approval, all others lower it at first.
~Keep an eye out for characters that have the trait that grants 1 Gravitas per turn, control or kill.
~There are retinues that can raise and lower Gravitas, assign them accordingly.
~There is an achievment for assassinating a member of your own sub faction.

• This guide was written based off gameplay in vanilla patch 5, the Civil War mechanic has been addressed in various patches.

For those who don't enjoy the Civil War mechanic.

1. Make sure the province your Capital is in produces at least -1 food.
2. Stop capturing settlements one settlement away from achieving Imperium 2.
3. Bring all Armies and Navies near the Capital to guard the next closest settlements, max the armies and navies out.
4. Leave the Civil War spawns a way to escape, preferably out to sea.
5. Have one army hide near the Capital in ambush stance out of the way but close enough to reach the capital in one turn.
6. Capture one more settlement and reach Imperium 2.
7. Force the Civil War to spawn by spamming political actions driving your approval to zero.
8. The Civil War spawns already starving due to the food deficit, don't fight them, they will take attrition losses.
9. The next turn they should have scattered, retake the capital with the hidden army.
10. Wait a few rounds and mop them up.

After the Civil War, the political mini game breaks down completely. You can now ignore sub factions all together as a Civil War can never spawn again.

Yes, in theory, you can win the game without ever having a Civil War. To do this you will need to make extensive use of the Military Alliance to meet your province holding quotas, and the hard part, maintain a political balance. By use of the Military Alliance you will never meet your max Imperium and therefore never have the Civil War forced.

Psychor: I can confirm it's possible to win game without civil war.

If you are having trouble getting Military Alliance treaties signed, you can check out my Diplomacy Guide.