Complex sentence: He then sailed east to Placentia, the French capital of Newfoundland, and began the Avalon Peninsula Campaign on November 1 during which he captured Saint John's and ruined most of the English fishing villages.
Split into simpler sentences: He then sailed east to Placentia, the French capital of Newfoundland, and began the Avalon Peninsula Campaign on November 1. On this expedition he captured Saint John's and ruined most of the English fishing villages.