Their kings were viewed as both gods and kings and the center of the universe. They were known as a warrior people who ruthlessly conquered neighboring countries. They used iron weapons, cavalry, couriers, signal fires, and spy networks as well as scare tactics and mass deportation to conquer others.Their control was more effective at the core and less effective in the peripheral parts of the empire. They consisted of free, land-owning citizens, farmers and artisans, and slaves. They preserved the knowledge inherited from older Mesopotamian societies and made original contributions to mathematics and astronomy. They maintained libraries that were attached to temples in the cities, such as the Library of Ashurbanipal in Ninevah.