Complex sentence: He attended the public schools, Francestown Academy, and Phillips Academy; he graduated from the United States Military Academy in 1872 and served in the Second Regiment, United States Infantry, as second lieutenant until 1877, when he resigned from the Army.
Split into simpler sentences: He attended the public schools, Francestown Academy, and Phillips Academy. He graduated from the United States Military Academy in 1872 and served in the Second Regiment, United States Infantry, as second lieutenant until 1877, when he resigned from the Army.