Civil war has a tendency to exponentiate. It doesn't take more than a few people to initiate it (assuming the rhetorical and attitude circumstances are favorable). The 1861 war started with one militia and one fort (really, depending on what historian you're talking to, it started with one religious fundamentalist family and a single raid on Harper's Ferry).

In 1861, people picnicked on a hillside to watch the first army-to-army fight of the war. By the end of the war, cities had been burned down.