The Republic by Plato Part 5 Page 74

in their natures; the one is expressive of what is internal and domestic, the other of what is external and foreign; and the first of the two is termed discord, and only the second, war.

That is a very proper distinction, he replied.

And may I not observe with equal propriety that the Hellenic race is all united together by ties of blood and friendship, and alien and strange to the barbarians?

Very good, he said.

And therefore when Hellenes fight with barbarians and barbarians with Hellenes, they will be described by us as being at war when they fight, and by nature enemies, and this kind of antagonism should be called war; but when Hellenes fight with one another we shall say that Hellas is then in a state of disorder