In the pre-classical age (8000 B.C.E. to 600 B.C.E.) the first states developed in core civilizations. Then, powerful cities imposed their rule on surrounding areas through conquest and the first empires were born. In the classical age (600 B.C.E. to 600 C.E.) empires grew on a massive scale through territorial conquest with large armies. The growing scale of these empires, along with their increased ethnic and cultural diversity, required more sophisticated methods of governance. They served as major hubs of transregional networks of trade, and they diffused culture, religion, technologies and disease. As empires acquired massive wealth, the unequal distribution of this wealth across social classes placed enormous pressure on the political and social order. Eventually, all of the classical civilizations could not deal with the problems created by their own internal or external crises. In most cases, the belief systems spawned in these empires left enduring cultural footprints even as the empires' political structures disintegrated.
