sacred power, energy or force." This is conceptualized in a kind of monistic pantheism as manifest in the supreme god , as well as a large pantheon of lesser gods and idealizations of natural phenomena such as stars and fire. Priests and educated upper classes held more monistic views, while the popular religion of the uneducated tended to embrace the polytheistic and mythological aspects. The Aztec empire's state-sanctioned religion meanwhile had to fulfill the spiritual obligations of the upper classes while maintaining their control over the lower classes and conquered populations. This was executed in grand public religious ceremonies, sponsorship of the most popular cults, and a relative degree of religious freedom. Rulers, if they are local or , or central Huetlatoani, were seen as representatives of the gods and therefore ruled by divine right. , or the principle of rulership, established that descent inherited this divine right. Political order was, therefore, also a cosmic order, and to kill a was to transgress that order. For this reason, whenever the Nahuas killed or otherwise removed a tlatoani from their station, their stead typically placed a relative and member of the same bloodline. The establishment of the office of Huetlatoani understood through the creation of another level of rulership, , standing in superior contrast to the lesser principle. A militaristic interpretation of Nahua religion, specifically a devout veneration of the sun god, Huitzilopochtli, guided expansion of the empire. Militaristic state rituals were performed throughout the year according to a ceremonial calendar of events, rites, and mock battles. The time period they lived in was understood as the , or Sun of Movement, which was believed to have been the final age after which humanity would be destroyed. It was under Tlacaelel that Huitzilopochtli assumed his elevated role in the state pantheon and who argued that it was through blood sacrifice that the Sun would be maintained and thereby stave off the end of the world. It was under this new, militaristic interpretation of Huitzilopochtli that Aztec soldiers were encouraged to fight wars and capture enemy soldiers for sacrifice. Though blood sacrifice was common in Mesoamerica, the scale of human sacrifice under the Aztecs was likely unprecedented in the region. Schematic of hierarchy Provincial structure Originally, the Aztec empire was a loose alliance between three cities: Tenochtitlan, Texcoco, and the most junior partner, Tlacopan. As such, they were known as the 'Triple