What does 楚河漢界 on the board mean?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws and is regression-tested against the official 110-diagram repetition casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it against the engine before publishing.
Direct answer
"Chu river, Han border". It refers to the boundary agreed between the kingdoms of Chu and Han during the contention that followed the fall of the Qin dynasty, around 203 BCE. It is decoration with a historical reference attached — boards without the inscription play identically.
It dates the decoration, not the game
The reference is to real events of the 3rd century BCE, which is why it is sometimes offered as evidence that the game is that old. It is not: the inscription was applied to a board that already existed, and the modern game is a Song-dynasty artefact roughly a thousand years later.
What the river does in play
Only two things. Elephants may never cross it, and soldiers gain sideways movement once they do. It blocks no lines, is not a rank you can stand on, and every other piece ignores it entirely.
Related questions
Do all boards have the inscription?
Most do, but not all. Nothing about play depends on it.
Does it prove the game is 2,200 years old?
No. It is a later decoration referencing an older event.
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