Complex sentence: The emperor Valerian took the throne in 253 but from the following year he was away from Rome fighting the Persians who had conquered Antioch, and he never returned, as he was taken captive and died a prisoner.
Split into simpler sentences: The emperor Valerian took the throne in 253 but from the following year he was away from Rome fighting the Persians who had conquered Antioch. He never returned as he was taken captive and died a prisoner.