Civil war.
Why do they call it civil war?
It us not that there is anything civil about any war, especially a civil war.
I can imagine something like this:
“Excuse me, old chap, but I’m afraid I have to shoot you.”
“No problem old boy, unless I get you first.
“Well it’s back to the trenches, toodle pip.”
It never happened like that. What we imagine as an age of chivalry with knights carrying a ladies favour into battle on their lances is very mush a fiction made up in Hollywood. War is nasty, war is bad, just occasionally war can be the least bad of a number of bad options, and only then when everything has been attempted to prevent a war. And even then war is a very bad thing indeed.
As for civil war – we need a new word to describe it.