Winning blow: rook to b7 (c7·3)
c9-05793naming 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.
A fork made possible by the Chess960 piece placement.
Winning tactic: there is a move that gains a decisive advantage — find it.
Difficulty 1290 ShuffleRating — club-player level.
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.
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.
This position hides a concrete tactic that wins material or mates. Start with the most forcing candidate moves — checks, captures and threats — and calculate each to a clear end before choosing; the winning line is usually the one the opponent cannot meet.
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, rook c1 c7, bishop e1 h1, knight f1 g1, pawn b2 c2 e2 f2 h3 a4 g4.
Black: king b8, queen d8, rook c8, bishop e8 h8, knight d7 g8, pawn e5 a6 g6 f7 h7.
14 white and 12 black pieces are on the board; the puzzle position arises after move 13.
The position in numbers
Black are ahead by 2 points of material (29 against 31; 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 13, with 38 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 7 pawns, Black 5. Files fully open (no pawns of either colour): d — natural highways for the rooks and queen.
The White king has 2 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
13. Rb7+ Ka8 14. Rxd7+ Kb8 15. Rxd8
Why it works
- Great move! rook to b7 keeps the pressure (+5.6).
- Spot on — rook to d7 (+5.8).
- Precise: rook to d8 is the top choice (+5.7).
- You win a piece — the queen.
- If instead Ka8, then Rxd7+ and you win the knight.
Move by move
- 13. Rb7+ — rook to b7 with check
- Ka8 — king to a8
- 14. Rxd7+ — rook to d7 (capture) with check
- Kb8 — king to b8
- 15. Rxd8 — rook to d8 (capture)
Types in this puzzle
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.
Only move
Everything else loses — find the only move that holds.
An only move is a position where everything loses except one single continuation. You cannot play "by hand" here: run through fundamentally different defenses — run away, block, trade, counterattack — and discard the ones that fail. The hallmark of these puzzles is that the obvious moves lose quickly while the solution often looks strange. First understand exactly what the threat is — then the one saving move reveals itself.
Rook fork
The rook attacks two targets along rank and file at the same time.
A rook fork attacks two targets from one square — one along the file, the other along the rank. Look for enemy pieces standing at a right angle to each other, both visible from a single safe square. This is bread and butter in endgames, where a rook check picks up loose pieces and pawns along the way. Test every rook check you have: does it also hit something valuable on the other line?
About this position
These pieces come from starting position #923.
SP-923 · RampartGuard — A wing king (b/g) with no knight on the a- or h-file.
The king starts on b1, the rooks on a1 and c1, the queen on d1.
From b1 the king makes the longest journey Chess960 allows when castling short: five squares to g1.
A bishop starts in the corner on h1: it has a single diagonal, which the g-pawn unlocks, running out to a8.
The pawn on b2 is defended by the king alone — the same soft spot f2 is in the classical setup.
The setup belongs to the RampartGuard family; read right to left it becomes position 33.
The engine's main line opens with a4.
Morozov Balance Index: 37 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +30 centipawns for White (depth 45, 400 000 000 nodes).
Explore position #923Provenance
Mined from the project's engine self-play games.
Verified by Stockfish at depth 20+.
Solution forcedness confirmed (verified).
Pack 009 · SP-923
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