Well, sadly, it's of course violence. The basic contract of government is you give up some liberty for safety (Hobbes), i.e. you don't go around robbing people, and the government will see that no one else goes around robbing you. But this sort of first form of government was inflexible, and if you wanted to change it you basically had to kill the people in charge. The chief innovation of liberal government was "self governance", and the trade there was "OK, we'll listen to you, you don't have to murder us to effect change". Practically everyone does this via some form of voting.

But as soon as that contract breaks down, i.e. the government stops listening to you, then that contract is breached and generally trouble starts. It gets (arguably) even worse if the government falls entirely, because then you get the kind of lawless marauding you had before any government.