Complex sentence: In command of the submarine "Trenchant" based at Trincomalee, Ceylon (now Sri Lanka), he took part in a number of operations in the East Indian and Pacific theatres that earned him his first DSO.
Split into simpler sentences: In command of the submarine HMS "Trenchant", based at Trincomalee, Ceylon (now Sri Lanka). He took part in a number of operations in the East Indian and Pacific theatres that earned him his first DSO.