Complex sentence: After the outbreak of the American Civil War, Sidney Randolph DeLong enlisted as a private at the Presidio, August 18,1861, and was mustered into Company C, 1st California Infantry August 26.
Split into simpler sentences: After the outbreak of the American Civil War, DeLong enlisted as a private at the Presidio, August 18,1861. He mustered into Company C, 1st California Infantry August 26.