Teotihuacan was a large Mesoamerican city at the height of its power in 450-600 CE. The city had a population of 125,000 to 150,000 inhabitants and was dominated by religious structures, including pyramids and temples where human sacrifice was carried out. The growth of Teotihuacan was made possible by forced relocation of farm families to the city and by agricultural innovations, including irrigation works and chinampas that increased production and thus supported a larger population. The elite lived in residential compounds separate from the commoners, and controlled the state bureaucracy, tax collection, and commerce. Teotihuacan appears to have been ruled by alliances of wealthy families rather than by kings. The military was used primarily to protect and expand long-distance trade and to ensure that farmers paid taxes or tribute to the elite. Teotihuacan collapsed around 750 CE. The collapse may have been caused by mismanagement of resources and conflict within the elite, or as a result of invasion.