By absorption of other cultural elements and by conquest the Aztec achieved a composite civilization, based on the heritage of Toltec and Mixteca-Puebla. They attained a high degree of development in engineering, architecture, art, mathematics, and astronomy. The Aztec calendar utilized a 260-day year and a 52-year time cycle. Aztec skill in engineering was evident in the fortifications of their island capital. The Aztec further developed sculpture, weaving, metalwork, ornamentation, music, and picture writing for historical records. Agriculture was well advanced and trade flourished.
The political and social organization was based on three castes—nobility, priesthood, and military and merchants. The priesthood was a powerful political as well as religious force. Aztec government was relatively centralized, although many conquered chiefs retained political autonomy; they paid tribute and kept commerce open to the Aztec. The Aztec had a large and efficient army. Prisoners of war were used for human sacrifice to satisfy the many gods of the Aztec pantheon, notably Huitzilopochtli, the chief god, who was god of war.