Aztec human sacrifice, 16th century. Illustration of a priest holding a spear while presiding over the sacrifice of a flower war captive whose heart is being removed. At upper left, incense is being burned in a holder on the steps of a temple. The Aztecs believed that human sacrifice ensured the Sun would rise again nourished by the hearts of men. The Aztec Empire (ruled by the Mexica) was an alliance of three city states that ruled in central Mexico from 1428 until their defeat by Spanish conquistadors in 1521. Artwork from a 19th-century copy of a 16th-century post-conquest codex and history of the Aztecs by Jesuit missionary Juan de Tovar.