Complex sentence: He set out from Plymouth on 15 November 1577, but bad weather threatened him and his fleet, who were forced to take refuge in Falmouth, Cornwall, from where they returned to Plymouth for repair.
Split into simpler sentences: He set out from Plymouth on 15 November 1577, but bad weather threatened him and his fleet. They were forced to take refuge in Falmouth, Cornwall, from where they returned to Plymouth for repair.