Reading An Introduction to Confucianism, which is not the typical historically linear treatment (i.e., Confucius → Han dynasty State Confucianism → Song dynasty Neo-Confucianism, etc.), and is also more comprehensive than most introductions (it’s over 350 pages). In case, the author notes that before the Han dynasty Confucianism was simply one of many contesting schools. It was during the reign of Hanwudi that Confucianism was integrated into the administrative ideological apparatus of the unified Chinese state, resulting in State Confucianism. It is famously known that the Legalist school, which was brought to preeminence by the students of the Confucian sage with the most “tragic vision,” Xunzi, attempted to expunge Confucianism during the Chin dynasty. The Chin dynasty is reviled throughout most of Chinese history (with the Maoists being an interesting exception) for its espousal of Legalism and rejection of the humanistic ethos at the heart of Confucianism, but, it is also acknowledged by modern scholars to have set the foundations for the dynastic system which fostered a resurrection of a unified Chinese imperial state after every political collapse. The Chin united China in a manner which set the template for all of Chinese history; by comparison, the Zhou dynasty which the early Confucians idolized was a primitive and feudal polity.
Many modern scholars would argue that the practical structural scaffolding of the Chinese state between the Chin and the early 20th century, a span of over 2,000 years, owed much to Legalism, even if the symbolic ideological core of the state was generally Confucian. And yet I can not help but wonder if China would ever have been unified, and its local identities subordinated to the center, if not for the blitzkrieg which was the Chin Legalist state. Like Stalinist Russia or Maoist China it seems likely that the Legalist phase had a “sell-by” date, the Chin dynasty collapsed almost immediately after the death of the First Emperor. A China where Confucian ideology marginalized Legalism early enough may have been one where China, like India or Europe, developed into a civilization of states, instead of a state which was coterminous with the civilization. State Confucianism may never have developed, and become entrenched as the foundational ethos of the bureaucratically oriented literati. The Confucian Age in China may have been an ancient period before the rise of Buddhist monarchies.
Addendum: Also recommended, The Early Chinese Empires: Qin and Han.