Complex sentence: In the Battle of the Hellespont Licinius'navy had been destroyed when his admiral, Abantus, had been outfought by Constantine's son the caesar Crispus, despite the latter's distinctly smaller fleet.
Split into simpler sentences: In the Battle of the Hellespont Licinius'navy had suffered a catastrophic defeat. His admiral, Abantus, had been outfought by Constantine's son the caesar Crispus, despite the latter's distinctly smaller fleet.