Complex sentence: At the end of the Second World War he remained in the Navy becoming a test pilot at the Empire Test Pilots' School and he saw further action during the Korean War, when he served aboard as Commander (flying).
Split into simpler sentences: At the end of the Second World War he remained in the Navy, becoming a test pilot at the Empire Test Pilots' School. He saw further action during the Korean War, when he served aboard as Commander (flying).