Winning blow: knight to b6 (c4·4)
c9-12154naming 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 1060 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 c1, queen e2, rook e1 f1, bishop c2 d2, knight c4, pawn b2 h2 c3 g3 a4 d4.
Black: king c8, queen g8, rook a8 e8, bishop d7 b8, knight g6 e7, pawn g4 a5 f5 d6 e6 b7.
13 white and 14 black pieces are on the board; the puzzle position arises after move 22.
The position in numbers
Black are ahead by 3 points of material (34 against 37; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on c1, the black king on c8.
It is White to move on move 22, with 40 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 6. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: e, f.
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
22. Nb6+ Kd8 23. Bb3 Nf8 24. Nxa8
Why it works
- Great move! knight to b6 keeps the pressure (+2.8).
- bishop to b3 develops smoothly.
- Precise: knight to a8 is the top choice (+3.4).
- You win a piece — the rook.
- If instead Kd8, then Bb3 and you stay on top.
Move by move
- 22. Nb6+ — knight to b6 with check
- Kd8 — king to d8
- 23. Bb3 — bishop to b3
- Nf8 — knight to f8
- 24. Nxa8 — knight to a8 (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.
Royal fork
A fork with check: the king must move, and the second piece is lost.
A royal fork is a fork with check — one of the two targets is the king itself. The check must be answered first, so nobody is left to rescue the second piece. Look for squares where your piece gives check and simultaneously attacks an undefended queen or rook. It is the most reliable fork of all, because your opponent literally has no choice.
About this position
These pieces come from starting position #760.
SP-760 · BastionGuard — Both knights begin inside the board while the king stands on c or f; a position and its mirror twin share this family.
The king starts on c1, the rooks on a1 and g1, the queen on h1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
The bishops stand on b1 and e1; their long diagonals reach h7 and a5 once the c- and d-pawns step aside.
One second-rank pawn starts with no defender at all: e2.
The setup belongs to the BastionGuard family; read right to left it becomes position 397.
The engine's main line opens with d4, putting a pawn straight into the centre.
Morozov Balance Index: 2 of 100 — class D — largest edge. Engine evaluation of the starting position: +61 centipawns for White (depth 46, 400 000 000 nodes).
In 50 self-play games White scored 56.0% (95% CI 42.3–68.8%).
Explore position #760Provenance
Mined from the project's engine self-play games.
Pack 006 · SP-760
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