The discovered attack
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Direct answer
A discovered attack moves one piece so that a second piece behind it attacks something. In xiangqi the cannon turns this idea upside down, because a cannon needs exactly one piece in the way to capture. Moving a screen away can switch a cannon off, and moving a piece into a line can switch one on.
The cannon works both ways
With a chariot the rule is the one chess players expect. Move the piece in front of it and the chariot's line opens.
With a cannon it runs the other way. A cannon with a clear line to a piece is not attacking it at all, because a cannon captures only by jumping exactly one screen. That produces two moves no other game has:
- Discovery by arriving. Put any piece, yours or a captured square's worth of the opponent's, into an empty line and a cannon behind it suddenly attacks whatever is beyond.
- Discovery by leaving. Move a screen out of the way and a cannon that was attacking stops. Defenders use this deliberately, and attackers forget it constantly.
Discovered check
The strongest form is when the piece revealed gives check, because the opponent must answer the check and cannot deal with whatever the moving piece did. The moving piece is free to take something, or to move somewhere it would never survive otherwise.
Double check, where the moving piece and the revealed piece both give check, is stronger still. Nothing can be blocked or captured out of a double check. The general has to move, which is why double check so often ends the game on the spot.
How to find them over the board
The habit is mechanical and takes a few seconds a move. Look for your own chariots and cannons that point at something valuable through exactly one of your pieces. Every one of those is a discovery waiting for the front piece to have somewhere useful to go.
Then reverse it. Look at the enemy chariots and cannons pointing through their own pieces at yours. Those are the moves you are about to be hit with.
Common mistakes
Moving the screen away by accident
Before any quiet move, check whether the piece you are moving is the screen holding one of your own cannon's threats together.
Playing the discovery too early
A discovered attack is worth more as a threat you can improve. If the revealed attack is not going anywhere yet, strengthen it first.
Forgetting the front piece can be captured
The moving piece often lands somewhere undefended. It is only safe if the check behind it is real.
Related questions
What is a discovered attack in xiangqi?
Moving one piece so that another piece behind it attacks something. With a chariot this means clearing the line. With a cannon it can mean the opposite, since a cannon needs one piece in the line to capture through.
What is double check?
A single move that gives check with two pieces at once, usually the moving piece and the one it uncovers. Neither check can be blocked or captured away, so the general must move.
Why are discovered attacks stronger in xiangqi?
Because the cannon can be switched on and off by moving other pieces, so lines open and close far more often than in chess. See how the cannon moves.
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