Complex sentence: Promoted to captain on 11 October 1850, he then took command of the steam frigate HMS "Amphion" in November 1853 and took part at the Battle of Bomarsund in August 1854 and the Bombardment of Sveaborg in August 1855 during the Crimean War.
Split into simpler sentences: Promoted to captain on 11 October 1850, he then took command of the steam frigate HMS "Amphion" in November 1853. He also took part at the Battle of Bomarsund in August 1854 and the Bombardment of Sveaborg in August 1855 during the Crimean War.