Complex sentence: A ground observer of the battle, Lieutenant Leser of the Coast Artillery, wrote a letter to Schoen's mother the day of his death, giving a vivid account of both the death and the atmosphere of a World War I dogfight.
Split into simpler sentences: A ground observer of the battle, Lieutenant Leser of the Coast Artillery, wrote a letter the day of Schoen's death. It was to Schoen's mother, and gives a vivid account of both Schoen's death and the atmosphere of a World War I dogfight.