What does the river do in xiangqi?
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
The river (楚河漢界) is the gap across the middle of the board. It affects exactly two pieces: elephants may never cross it, which locks them into permanent defence, and soldiers gain sideways movement once they cross, which roughly doubles their value. Every other piece ignores it entirely.
What it does not do
It does not block chariots, horses, cannons or generals, and it is not a rank you can stand on — it is the space between the 5th and 6th ranks, and pieces cross straight over it in a single normal move.
It does not stop check, and a cannon's screen can sit on either side of it.
Why the inscription
The characters 楚河 漢界 mean "Chu river, Han border" and refer to the boundary between the kingdoms of Chu and Han during the contention that followed the Qin dynasty. It is decoration with a story, not a rule — boards without the inscription play identically.
Related questions
Can a soldier go back across the river?
No. Soldiers never move backwards at all, in either half of the board.
Can an elephant ever cross?
Never, under any circumstances. It is the hardest limit on the board — see how the elephant moves.
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