In "Antigone", what was the reason for the battle in which Oedipus' sons were killed?

After Oedipus died in exile, both Eteocles and Polyneices were supposed to rule Thebes jointly. One was to rule one year and the other would rule the next year. However Eteocles refused to give up power to Polyneices once his year was over. So, Polyneices fled to Argos, raised an army, and attacked Thebes. Both brothers were killed in the battle. However, since Polyneices fought against Thebes, their uncle, Creon, who is now king over Thebes, refuses to allow Polyneices body to be buried. This was considered a sin against the gods and thus his sister, Antigone, decides to disobey her uncle's edict and to bury her brother.