What is a double check in xiangqi?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws for movement, checkmate and both repetition rulings: a side that forces a repetition by perpetual check or perpetual chase loses rather than drawing. The chase half has not been validated against the official casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it before publishing.
Direct answer
Two pieces giving check simultaneously, almost always from a discovered attack: the moving piece checks and uncovers a second checker behind it. One block or capture usually cannot deal with both, so the general normally has to move, and often it cannot. The exception is a chariot checking with a cannon behind it on the same line: a piece interposed between the chariot and the general blocks both.
Why it so often ends games
The general has nine points and several are occupied by its own pieces. When no single block or capture answers both checks, two of the three answers to check are gone, leaving only the one the confined palace makes hardest.
Setting one up
Look for a piece of yours that sits between one of your chariots or cannons and the enemy general (for a cannon, one of two pieces there), and that has a move which also gives check. That combination is a double check, and it is worth checking for every time a discovered attack is available.
Related questions
Can a cannon be part of a double check?
Yes, and it is common — the moving piece can step off a line where it was one of two pieces between the cannon and the general, or step onto an empty one as the screen, and give check itself as it lands.
Is double check always winning?
No, but it usually forces a general move, which is often enough to win material or mate.
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