Complex sentence: By the age of twelve, Perry had sailed with his father to the West Indies and by at the age of 13 was appointed a midshipman in the United States Navy on April 7,1799, aboard, commanded by his father who was a captain.
Split into simpler sentences: By the age of twelve, Perry had sailed with his father to the West Indies. He was appointed a midshipman in the United States Navy on April 7,1799, aboard, commanded by his father who was a captain.