Complex sentence: Leaving the island on 6 October, they transferred into their first prize, renamed the "Happy Return", and resumed their privateering cruise in spite of the war having ended in February and rendered their letter of marque invalid.
Split into simpler sentences: Leaving the island on 6 October, they transferred into their first prize, renamed the "Happy Return", and resumed their privateering cruise. This in spite of the war having ended in February, rendering their letter of marque invalid.