Complex sentence: He was graduated from the United States Military Academy at West Point, New York, in 1835 and entered the United States Army as first lieutenant the same year, serving until 1841 and attaining the rank of colonel.
Split into simpler sentences: He was graduated from the United States Military Academy at West Point, New York, in 1835. He entered the United States Army as first lieutenant the same year and served until 1841, attaining the rank of colonel.