What is the Cannon Across the Palace opening?
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
過宮炮 (Cannon Across the Palace) develops the cannon to the file directly in front of one of the advisors, for example 炮二平六, rather than straight down the centre. It avoids the sharp, well-studied theory of the Central Cannon and keeps options open for which wing to actually attack.
Why the cannon goes there instead of the centre
Sitting in front of an advisor's file, the cannon is not yet committed to a target, but it is one move away from swinging across to either flank once Black's setup reveals where the weaknesses are. That flexibility is the whole point of the system: information first, commitment second.
What it gives up for that flexibility
The Central Cannon creates an immediate, concrete threat down the middle that forces a specific reply. Cannon Across the Palace does not, so Black gets a freer hand to develop naturally in the opening moves rather than having to answer a direct threat right away. It suits players who prefer to develop first and commit to a plan once they can see the whole board.
Related questions
Is Cannon Across the Palace considered sound at a high level?
Yes, it is an established system with a long history, not a sideline or a trick.
Is it a good opening for a beginner?
The Central Cannon is usually recommended first because its plan is more concrete and teaches attacking play faster; see the Central Cannon.
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