The Han Dynasty is divided into two periods: the Western Han from 206 BC to 25 AD, centered in Chang'an; and the Eastern Han from 25 AD to 220 AD, centered in Luoyang. With vast territory, the Western Han was the most prosperous multi-national state in Asia at that time. Philosophically, the emperors of the Han Dynasty advocated the“Mandate of Heaven” to consolidate their rule. Centralized administration was institutionalized mid-dynasty during the rule of Emperor Wu. The “Silk Road,” a caravan and mercantile transport route stretching to West Asia, was established. This period is recognized as the Han “golden age,” during which the economy and culture flourished, and the empire’s political influence reached far into West Asia.