Complex sentence: The French repaired "Vengeance" and returned her to service but on 20 August 1800 the frigate, under the command of Captain David Milne, attacked her in the Mona Passage.
Split into simpler sentences: The French repaired "Vengeance" and returned her to service. Then on 20 August 1800 the frigate, under the command of Captain David Milne, attacked her in the Mona Passage.