Attack on the uncastled king: queen to b5 (c5)
c9-12923naming 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 1200 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.
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 c1, queen c5, rook a1 f1, pawn b2 c2 d2 g2 h2 a6.
Black: king c8, queen b5, rook b8 h8, knight e8, pawn e4 g5 h5 c7.
10 white and 9 black pieces are on the board; the puzzle position arises after move 21.
The position in numbers
Black are ahead by 1 points of material (25 against 26; 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 21, with 49 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 4. Files fully open (no pawns of either colour): f — natural highways for the rooks and queen. Half-open for White: e.
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
21. Qxb5 Rxb5 22. a7 Rb8 23. a8=Q Rxa8 24. Rxa8+
Why it works
- Great move! queen to b5 keeps the pressure (+5.1).
- Well found: pawn to a7 (+5.0).
- A natural move: pawn to a8.
- Great move! rook to a8 keeps the pressure (+5.0).
- You win a piece — the queen.
- If instead Rxb5, then a7 and you stay on top.
Move by move
- 21. Qxb5 — queen to b5 (capture)
- Rxb5 — rook to b5 (capture)
- 22. a7 — pawn to a7
- Rb8 — rook to b8
- 23. a8=Q — pawn to a8
- Rxa8 — rook to a8 (capture)
- 24. Rxa8+ — rook to a8 (capture) with check
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.
Clearance
Clear your own piece out of the way — with tempo — for the decisive blow.
Clearance is about your own piece standing in the way of the decisive blow — so you move it aside, or even throw it away. The key is to clear with tempo: jump off with a check, a capture or a threat, giving the opponent no time to regroup. The telltale sign: you see a crushing queen or rook move, but one of your own pieces blocks the line or occupies the square. Do not cling to it — a clearance sacrifice usually costs less than a missed attack.
Mate defense
Mate is threatened — parry it and stay on top.
Mate defense: your opponent is one move from mating you — but it is your turn, and that changes everything. Find the defense that kills the mating threat while keeping your advantage: often a check or a counter-threat that leaves no time for the mate. First name the exact square where the mate would land — otherwise you are defending blind. The mistake is playing a "defensive" move that does not actually remove the threat.
About this position
These pieces come from starting position #266.
SP-266 · BastionScout — The king starts one file off-centre, on c or f, and a knight begins in a corner.
The king starts on c1, the rooks on b1 and h1, the queen on g1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
The bishops stand on e1 and f1; their long diagonals reach a5 and a6 once the d- and e-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 597.
The engine's main line opens with Nc3, bringing the knight out to c3.
Morozov Balance Index: 57 of 100 — class B — balanced. Engine evaluation of the starting position: +26 centipawns for White (depth 45, 400 000 000 nodes).
In 50 self-play games White scored 53.0% (95% CI 39.5–66.1%).
Explore position #266Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-266
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