Attack on the uncastled king: knight to b7 (c5·24)
c9-06186naming 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.
An opening trap from this Chess960 starting position.
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 1610 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.
Early Chess960 traps punish natural but careless development. Look for a forcing move that exploits a piece the opponent has just placed on a poor square — a fork, a pin or a threat that wins material before either side is fully developed.
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 d1, rook c1 h1, bishop b1 g1, knight d3 c5, pawn a2 b2 c2 e2 f2 g2 d4 h4.
Black: king f8, queen d8, rook c8 h8, bishop b8 g8, knight d7 e8, pawn d5 h5 b6 a7 c7 e7 f7 g7.
16 white and 16 black pieces are on the board; the puzzle position arises after move 6.
The position in numbers
Material is level — 39 points of pieces on each side (pawn = 1, knight and bishop = 3, rook = 5, queen = 9).
The white king stands on f1, the black king on f8.
It is White to move on move 6, with 29 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 8 pawns, Black 8. No file is fully open, so the heavy pieces have to be pried in.
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
6. Nb7 c5 7. Nxd8
Why it works
- Great move! knight to b7 keeps the pressure (+5.5).
- Spot on — knight to d8 (+5.6).
- You win a piece — the queen.
- If instead c5, then Nxd8 and you win the queen.
Move by move
- 6. Nb7 — knight to b7
- c5 — pawn to c5
- 7. Nxd8 — knight to d8 (capture)
Types in this puzzle
First-rank tactic
Pieces still on their starting rank become targets of a first-rank strike.
The first-rank tactic: enemy pieces that never left their starting rank become targets themselves. Standing shoulder to shoulder, they block each other and are often defended by nobody. Look for a strike along the first or eighth rank — a rook or queen that breaks through harvests the undeveloped pieces. The mistake is treating the back rank as a safe "rear area": in Chess960 it can be the most vulnerable place on the board.
Queen trap
The strongest piece ventures too far — and cannot come back.
A queen trap catches the strongest piece after it ventures too far and finds no way home. The usual story is a queen grabbing a distant pawn — the classic poisoned pawn. The warning signs: the queen has few retreat squares, and enemy minor pieces cut them off one by one, gaining tempo with every move. Before your queen snacks on a pawn in enemy territory, count her escape routes — fewer than two means stay home.
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 #140.
SP-140 · BastionScout — The king starts one file off-centre, on c or f, and a knight begins in a corner.
The king starts on f1, the rooks on c1 and h1, the queen on d1.
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 b1 and g1; their long diagonals reach h7 and a7 once the c- and f-pawns step aside.
One second-rank pawn starts with no defender at all: b2.
The setup belongs to the BastionScout family; read right to left it becomes position 828.
The engine's main line opens with d4, putting a pawn straight into the centre.
Morozov Balance Index: 92 of 100 — class A — most balanced. Engine evaluation of the starting position: +12 centipawns for White (depth 46, 400 000 000 nodes).
Explore position #140Provenance
Mined from the project's engine self-play games.
Verified by Stockfish at depth 20+.
Solution forcedness confirmed (verified).
Pack 011 · SP-140
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