However, according to their philosophy, the one who gave life should also receive it. Since the heart is the symbol and vessel of life, the hearts of living people and animals were sacrificed to the sun god. Through these sacrifices, the sun kept his strength and was able to continue his journey through the sky. These sacrifices were not of a religious kind, but more of a magical kind. They were not meant to please or propitiate the sun, but only to renew his strength in the sense of warmth, light and motion.
To meet the demand of continuing human sacrifices to feed the sun god, each year the Aztec made war on the neighboring tribes. Great numbers of prisoners taken in these wars were slain on the altars of Ipalnemohuani. This cruel system caused the death of an immense number of people, and is considered one of the bloodiest and most horrible examples of human sacrifice in history.