Complex sentence: His only son was a lieutenant in the Fleet Air Arm; he also served in the Second World War and was killed travelling aboard HMS "Glorious" when the ship was attacked and sunk by the German battleships and off Norway on 8 June 1940.
Split into simpler sentences: His only son was a lieutenant in the Fleet Air Arm and also served in the Second World War. He was killed travelling on board HMS "Glorious" when the ship was attacked and sunk by the German battleships and off Norway on 8 June 1940.