Complex sentence: Stephen Russell Mallory (c.1812-November 9,1873) was the Confederate Secretary of the Navy during the American Civil War, and was considered one of President Jefferson Davis's ablest cabinet officers.
Split into simpler sentences: Stephen Russell Mallory (c.1812-November 9,1873) was a United States politician and the Confederate Secretary of the Navy during the American Civil War. Mallory was considered one of President Jefferson Davis's ablest cabinet officers.