Attack on the uncastled king: queen to b8 (d6·2)
c9-26632naming 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.
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
Winning tactic: there is a move that gains a decisive advantage — find it.
Difficulty 1700 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.
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.
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 g1, queen d6, rook e1 g3, bishop a4, knight b3, pawn a2 h2 e4 f4.
Black: king f8, queen c4, rook e7 h8, bishop b6 g8, knight b8, pawn g2 d4 f6 a7 g7.
10 white and 12 black pieces are on the board; the puzzle position arises after move 20.
The position in numbers
Black are ahead by 4 points of material (29 against 33; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on g1, the black king on f8.
It is White to move on move 20, with 49 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 4 pawns, Black 5. Files fully open (no pawns of either colour): b, c — natural highways for the rooks and queen. Half-open for White: d, g.
Black hold the bishop pair, an edge in open lines. 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
20. Qxb8+ Kf7 21. Nc5 d3 22. Bb3 Qxb3 23. axb3
Why it works
- Great move! queen to b8 keeps the pressure (+3.5).
- Well found: knight to c5 (+3.6).
- Strong! bishop to b3 is the sharp choice (+3.7).
- Great move! pawn to b3 keeps the pressure (+4.0).
- You win a piece — the queen.
- If instead Kf7, then Nc5 and you win the knight.
Move by move
- 20. Qxb8+ — queen to b8 (capture) with check
- Kf7 — king to f7
- 21. Nc5 — knight to c5
- d3 — pawn to d3
- 22. Bb3 — bishop to b3
- Qxb3 — queen to b3 (capture)
- 23. axb3 — pawn to b3 (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.
Winning blow
Find the strike that wins material by force.
A winning blow is a forced material gain that does not fit a single textbook motif. The general tactical recipe applies: spot loose pieces, an awkwardly placed king, overloaded lines. Go through the forcing moves in order of violence — checks, captures, threats — because most combinations start with one of them. Do not judge by feel: calculate the concrete line until the outcome is beyond doubt.
Counter-strike
Don't defend — answer the threat with a bigger one.
The counter-strike: instead of defending against the threat, you answer with a bigger threat of your own. While your opponent grabs a pawn, you deliver mate — the arithmetic favors you. Look for a counter when direct defenses fail: do you have a check, an attack on the queen, a mating threat? The beginner's error is meeting every threat with a reflexive defense without checking the counterattacking resources first.
About this position
These pieces come from starting position #45.
SP-45 · BastionScout — Off-centre king plus a rim knight (a/h): 168 positions carry this shape.
The king starts on f1, the rooks on e1 and h1, the queen on c1.
Castling ends where it always does: king to g1 and rook to f1 on the short side, king to c1 and rook to d1 on the long one.
The bishops stand on d1 and g1; their long diagonals reach h5 and a7 once the e- and f-pawns step aside.
One second-rank pawn starts with no defender at all: a2.
The setup belongs to the BastionScout family; read right to left it becomes position 920.
The engine's main line opens with e4, putting a pawn straight into the centre.
Morozov Balance Index: 34 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +31 centipawns for White (depth 47, 400 000 000 nodes).
Explore position #45Provenance
Mined from the project's engine self-play games.
Pack 013 · SP-45
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