Complex sentence: Carthaginian cavalry carried out Hannibal's instructions well and there was no sign of Roman cavalry on the battlefield and once they were far enough away, they turned and attacked the Roman cavalry but were routed in the end.
Split into simpler sentences: Carthaginian cavalry carried out Hannibal's instructions well and there was no sign of Roman cavalry on the battlefield. Once they were far enough away, they turned and attacked the Roman cavalry but were routed in the end.