Complex sentence: He was about to start for Cappadocia against the Goths when he was assassinated, together with Hairan, by his nephew Maeonius; there is no reason to suppose that this deed of violence was instigated from Rome.
Split into simpler sentences: He was about to start for Cappadocia against the Goths when he was assassinated, together with Hairan, by his nephew Maeonius. There is no reason to suppose that this deed of violence was instigated from Rome.