Attack on the uncastled king: bishop to b5 (e2·8)
c9-25527naming 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.
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.
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 f1, rook a1 d1, bishop e2, knight c2, pawn f2 e3 b4 h4.
Black: king c8, queen b5, rook b8 d8, bishop a8, knight d6 g8, pawn g6 a7 c7 d7 f7 h7.
10 white and 13 black pieces are on the board; the puzzle position arises after move 17.
The position in numbers
Black are ahead by 5 points of material (29 against 34; 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 17, with 34 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 4 pawns, Black 6. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: a, c, d, g.
The White king has 3 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
17. Bxb5 Nxb5 18. Ra5 Bc6 19. Qc4 Ne7 20. Qxf7
Why it works
- Great move! bishop to b5 keeps the pressure (+3.0).
- rook to a5 develops smoothly.
- Precise: queen to c4 is the top choice (+2.7).
- Best move. queen to f7 is exactly what the engine plays (+2.9).
- You win a piece — the queen.
- If instead Nxb5, then Ra5 and you win the queen.
Move by move
- 17. Bxb5 — bishop to b5 (capture)
- Nxb5 — knight to b5 (capture)
- 18. Ra5 — rook to a5
- Bc6 — bishop to c6
- 19. Qc4 — queen to c4
- Ne7 — knight to e7
- 20. Qxf7 — queen to f7 (capture)
Types in this puzzle
Relative pin
A piece shields a more valuable one behind it — moving it loses material.
In a relative pin the piece shields not its king but something valuable behind it, usually the queen. Moving is legal but costly, because the piece behind falls. Look for three units on one line: your long-range piece, a cheaper enemy piece, and an expensive one hiding behind. Beware the classic trap — a relatively pinned piece can still move with check or a bigger threat, so verify before you cash in.
Uncastled king
The king lingered in the middle — punish the delay.
Punishing the uncastled king: your opponent delayed castling, and now his king is stuck on its starting square under fire. In Chess960 this is deadlier than in classical chess — the king may start in the center or near the edge, and the familiar defensive setups simply do not apply. The signs: the victim still holds castling rights, and the files toward his king are half-open. Open lines before the king manages to hide.
Decoy
A sacrifice lures the king or a piece onto a fatal square.
A decoy is the mirror image of deflection: you sacrifice to drag the king or a piece onto a fatal square. The classic is a queen or rook sac whose capture pulls the king into a knight fork, a discovered check or mate. Find the square where the target will be hit, then find the offer it cannot refuse. Calculate to the very end — a decoy only works when the follow-up is forced.
About this position
These pieces come from starting position #931.
SP-931 · BastionGuard — The king starts one file off-centre, on c or f, with neither knight in a corner.
The king starts on c1, the rooks on b1 and d1, the queen on f1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
The second rank carries 2 pawns with no defender at all: a2, h2.
The setup belongs to the BastionGuard family; read right to left it becomes position 19.
The engine's main line opens with g4.
Morozov Balance Index: 47 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +27 centipawns for White (depth 45, 400 000 000 nodes).
Explore position #931Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-931
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