China is located between Russia, Southeast Asia, India, and Central Asia with over 9,000 miles of coastline in the Yellow, East and South China Seas.
It’s a country of deep geographic divisions, particularly between the arid highlands, and the fertile lowlands which are home to the ethnic Han Chinese core where more than a billion people live.
Traditionally threats to the core came from the borderlands, so past rulers have tried to push its borders outwards and integrate the highlands as strategic buffer zones.
However, keeping control of the core means that the individual regions must be united, despite their differences like dialects, and interests.
There are cycles of unity and fragmentation in Chinese history from strong periods when the core could maintain the buffers to weak ones when it fragmented and lost control of the borderlands.