How do a horse and cannon work together 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
They are the classic pair because the horse can be the cannon's screen while simultaneously covering escape points. That is exactly the 馬後炮 (horse behind cannon) pattern: the horse sits in front of the general, the cannon behind it on the same line, and the general has nowhere to go.
Why they complement each other
The cannon needs a screen and the horse needs a partner. Neither can mate alone — a lone cannon cannot even give check — but together they force mate against a bare general.
The horse also covers the two points beside the general that the cannon's line does not, which is the whole of the mate.
Order of arrival
The horse almost always goes first. It takes three or four moves to reach the point in front of the enemy palace and is hard to dislodge once there; the cannon can swing onto the line in a single move. That is why the mate so often appears suddenly.
Related questions
Can horse and cannon mate a bare general?
Yes, this is one of the standard winning material combinations.
What beats the pair?
A full defence of two advisors and two elephants usually holds. See advisors and elephants.
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