Complex sentence: He took part in a major action against pirates off Candia in June 1826 and subsequently served as a midshipman and mate in the brig HMS "Columbine", the frigate HMS "Undaunted" and then the battleship HMS "St Vincent" in home waters.
Split into simpler sentences: He took part in a major action against pirates off Candia in June 1826. He subsequently served as a midshipman and mate in the brig HMS "Columbine", the frigate HMS "Undaunted" and then the battleship HMS "St Vincent" in home waters.