Attack on the uncastled king: rook to d8 (d6·2)
c9-25206naming tag (square·N)Opens in the app if installed, otherwise downloads the APK.
The tactical motive
Chess960 twist: use the unusual starting setup of the pieces.
Mate in 3: a forced sequence that ends in checkmate.
A fork made possible by the Chess960 piece placement.
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
Difficulty 1630 ShuffleRating — for advanced tacticians.
White to move — find the best continuation
How to recognize this tactic
In Chess960 the pieces start on unfamiliar squares, so tactics appear earlier and from unusual angles. Do not trust classical patterns — read the actual lines of the bishops, the rooks and the queen from where they really stand in this position.
In a mate in three every move must be forcing; the defender should never get a free tempo. Find the check or threat that herds the king, calculate the single defence to each, and confirm the net closes on the third move.
A set-up fork needs one preparing move before the fork lands — a check that drives the king onto the forking square, or a capture that lines the targets up. Find the preparation first, then the fork it makes possible.
An uncastled king in the centre is a standing target. Look for ways to open the central files and diagonals against it with checks and threats before it can shelter — every tempo the king spends in the middle is a chance for a combination.
General method: before you move, list the forcing candidates — every check, every capture, every direct threat — and calculate those first. The solution to a tactic is almost always among them.
Position on the board
White: king b1, queen d1, rook h1 d6, bishop f1, knight h3, pawn c2 g2 h2 f3 b4 a5 b5.
Black: king b8, rook a8 h8, bishop g4, knight g8, pawn h5 a7 f7 g7.
13 white and 9 black pieces are on the board; the puzzle position arises after move 20.
The position in numbers
White are ahead by 12 points of material (32 against 20; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on b1, the black king on b8.
It is White to move on move 20, with 39 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 7 pawns, Black 4. Files fully open (no pawns of either colour): d, e — natural highways for the rooks and queen.
The White king has 4 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
20. Rd8+ Kb7 21. a6+ Kc7 22. Qd6#
Why it works
- Best move. rook to d8 is exactly what the engine plays (#2).
- Spot on — pawn to a6 (#1).
- Precise: queen to d6 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Kb7, then a6+ and you stay on top.
Move by move
- 20. Rd8+ — rook to d8 with check
- Kb7 — king to b7
- 21. a6+ — pawn to a6 with check
- Kc7 — king to c7
- 22. Qd6# — queen to d6 and it is checkmate
Types in this puzzle
Supported queen mate
The queen delivers mate face to face, protected by a friend.
The supported queen mate is the most common pattern of all: the queen lands next to the king and mates because a friendly piece or pawn protects her. The king is helpless — capturing is impossible, and the queen covers every neighboring square herself. Hunt for a protected square beside the enemy king: a knight, bishop or pawn eyeing it turns her invasion into mate. Verify one thing — that the square really is defended, or the king eats her.
Setup fork
The random setup allows a fork that classical chess never sees.
A setup fork is a double attack that exists only because of the unusual starting squares — in classical chess these targets never stand side by side. Look for pairs of undefended pieces on your opponent's back rank and for squares from which a knight or pawn hits both at once. Such forks usually appear within the first moves, before the pieces disperse. In every new position, note right away which starting pieces are defended by no one.
Mate in 3
A forced checkmate in three moves.
Mate in three is a forced staircase: each of your moves narrows the opponent's choices, and the third one ends the game. Look for the start among checks and sacrifices — quiet first moves are rare in mating problems, but deliciously sneaky. Keep the tree in your head: every defense gets its own branch. Do not stop calculating after move two — see the final mating picture with your own eyes.
About this position
These pieces come from starting position #710.
SP-710 · RampartGuard — A b- or g-file king and two knights on inner files (b–g).
The king starts on b1, the rooks on a1 and h1, the queen on d1.
From b1 the king makes the longest journey Chess960 allows when castling short: five squares to g1.
The bishops stand on c1 and f1; their long diagonals reach h6 and a6 once the d- and e-pawns step aside.
One second-rank pawn starts with no defender at all: f2.
The setup belongs to the RampartGuard family; read right to left it becomes position 438.
The engine's main line opens with e4, putting a pawn straight into the centre.
Morozov Balance Index: 21 of 100 — class D — largest edge. Engine evaluation of the starting position: +36 centipawns for White (depth 47, 400 000 000 nodes).
Explore position #710Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-710
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