Civil unrest/civil war

[Jack American]

Some time ago, I played a game where I attacked and took over the capital city of an AI opponent and the best thing happened. His civ went into unrest and his nation split into two. What was up with his civ and what are the parameters to make this occur? I haven't been able to make it happen again since. I've set up games in cheat mode to experiment with different scenarios but to no avail. Anyone know how I can get this to occur again?

[Hueij]

IIRC the civ in question must be the biggest one AND there must be room for a new civ (there can't be more than 7 civs at the same time).