90s Star Wars EU Writers: "So is the clone wars about two different clone armies fighting each other, is it a clone rebellion? What is it?"
90s George Lucas:

You know, the Great Offscreen War! Like the one in Lord of the Rings where Sauron was defeated by the alliance of Elf and Man, the one before the start of Lord of the Flies, that tiff between Scotland and Norway before Macbeth begins, and countless more examples that weren't around yet by 1977 (Castlevania's 1999 conflict, Mega Man's Elf Wars, Doctor Who's Last Great Time War, etc).