Complex sentence: In 1566 Pedro Menéndez de Avilés, founder of St. Augustine, made contact with the Calusa and struck an uneasy peace with their leader, Caluus, or Carlos.
Split into simpler sentences: In 1566 Pedro Menéndez de Avilés, founder of St. Augustine, made contact with the Calusa. He struck an uneasy peace with their leader Caluus, or Carlos.