Attack on the uncastled king: pawn to b6 (c5·23)
c9-21179naming 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 1060 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.
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 f2, rook b1 h1, bishop d1 e1, knight a1 c1, pawn a2 d2 e2 g2 h2 f3 c4 c5.
Black: king f8, queen g8, rook b8 h8, bishop b6 g6, knight a8 c8, pawn d6 f6 a7 b7 e7 g7 h7.
16 white and 15 black pieces are on the board; the puzzle position arises after move 6.
The position in numbers
White are ahead by 1 points of material (39 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 6, with 34 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 8 pawns, Black 7. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: b.
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
6. cxb6 Bxb1 7. bxa7 Nxa7 8. Qxa7
Why it works
- Great move! pawn to b6 keeps the pressure (+5.0).
- Well found: pawn to a7 (+4.8).
- Strong! queen to a7 is the sharp choice (+4.9).
- You reach a winning position (+4.9).
- If instead Bxb1, then bxa7 and you stay on top.
Move by move
- 6. cxb6 — pawn to b6 (capture)
- Bxb1 — bishop to b1 (capture)
- 7. bxa7 — pawn to a7 (capture)
- Nxa7 — knight to a7 (capture)
- 8. Qxa7 — queen to a7 (capture)
Types in this puzzle
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.
Counter-strike
Don't defend — answer the threat with a bigger one.
The counter-strike: instead of defending against the threat, you answer with a bigger threat of your own. While your opponent grabs a pawn, you deliver mate — the arithmetic favors you. Look for a counter when direct defenses fail: do you have a check, an attack on the queen, a mating threat? The beginner's error is meeting every threat with a reflexive defense without checking the counterattacking resources first.
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 #169.
SP-169 · BastionScout — A c- or f-file king with at least one knight out on the edge.
The king starts on f1, the rooks on b1 and h1, the queen on g1.
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 e1; their long diagonals reach h5 and a5 once the e- and d-pawns step aside.
Every pawn on the second rank is defended from the very first move.
The setup belongs to the BastionScout family; read right to left it becomes position 793.
The engine's main line opens with c4.
Morozov Balance Index: 34 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +31 centipawns for White (depth 46, 400 000 000 nodes).
Explore position #169Provenance
Mined from the project's engine self-play games.
Pack 006 · SP-169
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