Attack on the uncastled king: pawn to b5 (a4·36)
c9-21174naming 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 f1, queen h1, rook a1 g1, bishop d1 e1, knight d3, pawn b2 c2 d2 g3 a4 f4 h4.
Black: king f8, queen h7, rook a8 g8, bishop d8 e8, knight b5 c6, pawn a5 h5 b7 c7 d7 e7 g7.
14 white and 15 black pieces are on the board; the puzzle position arises after move 11.
The position in numbers
Black are ahead by 3 points of material (35 against 38; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on f1, the black king on f8.
It is White to move on move 11, with 33 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 7 pawns, Black 7. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: e.
The White king has 4 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
11. axb5 Nd4 12. Qxb7 Bg6 13. Nf2 e6 14. Qxa8
Why it works
- Great move! pawn to b5 keeps the pressure (+3.9).
- Spot on — queen to b7 (+4.1).
- Precise: knight to f2 is the top choice (+3.9).
- Best move. queen to a8 is exactly what the engine plays (+4.3).
- You win a piece — the rook.
- If instead Nd4, then Qxb7 and you win the knight.
Move by move
- 11. axb5 — pawn to b5 (capture)
- Nd4 — knight to d4
- 12. Qxb7 — queen to b7 (capture)
- Bg6 — bishop to g6
- 13. Nf2 — knight to f2
- e6 — pawn to e6
- 14. Qxa8 — queen to a8 (capture)
Types in this puzzle
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.
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.
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.
About this position
These pieces come from starting position #473.
SP-473 · BastionGuard — Off-centre king (c/f), no knight on the a- or h-file.
The king starts on f1, the rooks on a1 and g1, the queen on h1.
Castling short simply swaps the two pieces: the king on f1 and the rook on g1 trade places.
The bishops stand on d1 and e1; their long diagonals reach h5 and a5 once the e- and d-pawns step aside.
One second-rank pawn starts with no defender at all: b2.
The setup belongs to the BastionGuard family; read right to left it becomes position 681.
The engine's main line opens with d4, putting a pawn straight into the centre.
Morozov Balance Index: 7 of 100 — class D — largest edge. Engine evaluation of the starting position: +47 centipawns for White (depth 42, 400 000 000 nodes).
Explore position #473Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-473
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