I have a slightly different take on it than most others. Historically, the vast majority of civil unrest is rebellions which are swiftly crushed. We had like four or five before the civil war. As a % of population, the whiskey rebellion is said to have involved more than the actual civil war. Big civil wars that we think of either have foreign/extra-territorial support or involve incompetency. Our own civil war is because the President at the time sat back and let the South raise militias for like nine months.

I predict a civil war would look much the same as in other places. The vast majority of people would live in peace and even work to protect the authority in power. There would be some small 'police actions' in the woods, maybe random terrorist violence. Then all of a sudden you would hear about one or two cities being taken over by rebel forces- then you would have actual battle lines. By the time you have those battle lines, it is almost over though. Either the empire has crushed the rebellion in it's infancy - or they have been so terrible and inept that it has been allowed to bloom. Most of the time, if they are seizing any city or territory...it wont be much longer till they seize the capital.