Attack on the uncastled king: knight to b3 (d2·2)
c9-23688naming 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 g1, queen a1, rook b1 h1, bishop e2 f2, knight e1 d2, pawn g2 h2 f3 c4 e5.
Black: king f8, queen a8, rook b3 h8, bishop c6 d8, knight d7 e8, pawn a4 f5 e6 c7 g7 h7.
13 white and 14 black pieces are on the board; the puzzle position arises after move 15.
The position in numbers
Black are ahead by 1 points of material (36 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 g1, the black king on f8.
It is White to move on move 15, with 32 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 5 pawns, Black 6. Files fully open (no pawns of either colour): b, d — natural highways for the rooks and queen. Half-open for White: a.
The White king has 1 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
15. Nxb3 axb3 16. Qxa8 Bxa8 17. Nd3 Be7 18. Rxb3
Why it works
- Great move! knight to b3 keeps the pressure (+3.8).
- Spot on — queen to a8 (+3.7).
- A natural move: knight to d3.
- Best move. rook to b3 is exactly what the engine plays (+3.6).
- You win a piece — the queen.
- If instead axb3, then Qxa8 and you win the queen.
Move by move
- 15. Nxb3 — knight to b3 (capture)
- axb3 — pawn to b3 (capture)
- 16. Qxa8 — queen to a8 (capture)
- Bxa8 — bishop to a8 (capture)
- 17. Nd3 — knight to d3
- Be7 — bishop to e7
- 18. Rxb3 — rook to b3 (capture)
Types in this puzzle
Winning exchange
A forced series of captures on one square ends in your favour.
A winning exchange is a forced series of captures on one square that leaves you ahead in material. It is pure arithmetic: count the attackers and defenders of the square and note the value of every piece in the queue. Capture in the right order — cheap pieces first, expensive ones later — or a winning trade turns into a losing one. The classic error is stopping the count halfway and missing the opponent's final recapture.
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 #397.
SP-397 · BastionGuard — The king starts one file off-centre, on c or f, with neither knight in a corner.
The king starts on f1, the rooks on b1 and h1, the queen on a1.
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: d2.
The setup belongs to the BastionGuard family; read right to left it becomes position 760.
The engine's main line opens with f4.
Morozov Balance Index: 31 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +32 centipawns for White (depth 44, 400 000 000 nodes).
Explore position #397Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-397
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