Shyrramar and judgement,
Good idea!!
I just want to add something
There are 2 possible scenarios for each civil war.
1. Coup - A takeover of leadership. There is internal but not military struggle. This is portrayed in Civ as the peaceful revolution (although in reality it is not). However, since the character we controlled is the most brilliant man of the nation, he/she always win in a coup. Plus, he/she is immortal.
2. Military Coup (civil war) - the rebel cannot takeover internally, so he relies on violent methods, which result in a civil war.
The conclusion of a civil war is either
a. Peaceful coexistence ¡V the rebel gain independence. You signed a peace treaty
b. Overthrown your government ¡V Game over. You lost the entire empire to the rebel
c. You quelled the rebels ¡V you regain the cities you lost. However, beware of your culture and the citizen mood, because the unhappy citizens can turn into resistors.
The culture that would affect the defection probability should NOT be the culture of the city in question, but the culture of other cities near it. Take the culture of the another city and divide it by distance. Being in the trade-network would decrease the possibility of defection significantly. There is no point in the idea that a distant and lone city with 1000 culture points should not break away of your nation - on the contrary: they would be very aware of their own identity.
This is a nice idea. This is what I think should be the case. Defection probability is calculated from the sum of citizen happiness and the average of X% of culture points per distance from each city of the empire per city. (In this case, a city of more culture points can exert the effect of the culture in a longer range). Equation: (Y% of total unhappy citizen + (X% £U (Culture points / distance of each city in the empire) / (number of city)) = Z, where Y= a constant value and X= a constant value. Once Z lowers to a pre-determine value, an unhappy citizen becomes a resistor like what judgement said (also, as Shyrramar said, the Z value should be very low and hard to achieve, and X and Y should be adjusted accordingly). Once that happens, a resistor increases Y constant of the nearby city by some factor (everyone fears terrorists). This increases unhappiness of the nearby cities. Unhappiness + the lack of cultural influences from surrounding cities using the above equation further create more resistors. Each (or a determined turns) turn, one unhappy citizen is converted to a resistor (one happy citizen to a content citizen). When 10% (subject to determination) of total citizens become resistors, civil disobedience can occur (there is not enough people to work on the farm). However, Military presence can prevent or suppress the civil disobedience. However, as the number of resistors increase to 50% of total citizens (you must be ignoring the situation!!!), the amount of military presence you need in order to suppress the resistors become exponential. You won¡¦t have enough military units to prevent the overthrown of your government.
How does one lose the city? I like Shyrramar¡¦s #1, but I also modified it a little bit. When the number of resistor reachs 4 units (subject to determination), and there aren¡¦t enough military presence (like what I just said), all four resistors become rebel conscripts or regular defenders. All of your units that once occupied the city are then kicked out of the city with one or two (elite) Health Points. Your will lose the city. This will significantly decrease the Z value of the cities surrounding it. If the cities don¡¦t have enough points to overcome the minimum Z, these cities will convert more citizens to resistors each turn, and these resistors will eventually rebel and cause a flip. This chain reaction will spread until it is stopped by the boundary cities that have the Z value higher than the requirement. This chain reaction can be stopped if you sign a peace treaty with the rebel. Once you sign the treaty, the rebel states become one new nation.
If you choose to have a war, you can attack the rebel city with the troops that were kicked out. However, since they have low health points, you will be risking the life of these troops. If you want to send in the reinforcements, they will have to cross the border, which will cost at least one turn (more turns if the rebel destroys the roads). You must be fast enough to get back the city or that the cities surrounding the rebel city will be converted (if they are also unhappy and have low cultural influences).
Of course, the details need to be adjusted to fit the gaming.