Historians usually divide the history of China into three rough periods, “Ancient China”, “Imperial China”, and “Modern China”. I don’t think this is quite right. This is similar to how historians divide the history of Europe and the Mediterranean into “Classical Civilization” and “Western Civilization”. It’s clear that Classical Civilization and Western Civilization are different civilizations, that
Many historians of China group Qin/Han in with the Warring States era. This is fairly common.
Historians also tend to divide the imperial period into "early" and "late." The exact point of this transition is up for debate--there is a famous book titled <i>The Song-Yuan-Ming Transition in Chinese History</i> that subsumes the controversy by making the transition point three dynasties long. But the point is generally solid: if you compare the Qing or Ming with the Tang you can see these differences: one empire is meritocratic, one aristocratic; one is commercial and (relatively) urban, the other has its wealth invested almost purely in land; one one is demographically weighted towards the south, the other towards the north; one is doctrinaire neoconfuncian, with all that entails; the other sees a competition between Buddhist, Daoist, and Confucian elements, with the first of these claiming immense privileges.
If you take Buddhism to be the thing that divides ancient from medieval, then ending the classical era around the fall of the Han makes sense.
On the other hand, if you care more about the political institutions, economic foundations, and lines of nobility, the transition ought to be Qin/Han. Wang Aihe has an interesting paper on how the Han represented a social revolution in the leadership of China (whereas both the Qin and Xiangyu represented continuity with the old noble houses): https://www.jstor.org/stable/41645568
Many historians of China group Qin/Han in with the Warring States era. This is fairly common.
Historians also tend to divide the imperial period into "early" and "late." The exact point of this transition is up for debate--there is a famous book titled <i>The Song-Yuan-Ming Transition in Chinese History</i> that subsumes the controversy by making the transition point three dynasties long. But the point is generally solid: if you compare the Qing or Ming with the Tang you can see these differences: one empire is meritocratic, one aristocratic; one is commercial and (relatively) urban, the other has its wealth invested almost purely in land; one one is demographically weighted towards the south, the other towards the north; one is doctrinaire neoconfuncian, with all that entails; the other sees a competition between Buddhist, Daoist, and Confucian elements, with the first of these claiming immense privileges.
If you take Buddhism to be the thing that divides ancient from medieval, then ending the classical era around the fall of the Han makes sense.
On the other hand, if you care more about the political institutions, economic foundations, and lines of nobility, the transition ought to be Qin/Han. Wang Aihe has an interesting paper on how the Han represented a social revolution in the leadership of China (whereas both the Qin and Xiangyu represented continuity with the old noble houses): https://www.jstor.org/stable/41645568