Attack on the uncastled king: pawn to a4 (b3·10)
c9-06086naming 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 780 ShuffleRating — for beginners taking their first steps in Chess960 tactics.
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 b2, queen e1, rook d1 h1, bishop f1 e3, knight a1, pawn c2 g2 a3 b3 c3 f3 e4 h4.
Black: king c8, queen e7, rook b8 h8, bishop f7, knight a4 c6, pawn e5 h5 d6 f6 a7 b7 c7 g7.
15 white and 15 black pieces are on the board; the puzzle position arises after move 12.
The position in numbers
Material is level — 36 points of pieces on each side (pawn = 1, knight and bishop = 3, rook = 5, queen = 9).
The white king stands on b2, the black king on c8.
It is White to move on move 12, with 4 legal replies to weigh — only the line that keeps the advantage solves the puzzle. White are in check right now, so every reply must answer the check.
White keeps 8 pawns, Black 8. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: d.
White hold the bishop pair, an edge in open lines. 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
12. bxa4 Na5 13. Nb3 Nc4+ 14. Bxc4
Why it works
- Great move! pawn to a4 keeps the pressure (+3.2).
- knight to b3 develops smoothly.
- Precise: bishop to c4 is the top choice (+3.2).
- You win a piece — the knight.
- If instead Na5, then Nb3 and you win the knight.
Move by move
- 12. bxa4 — pawn to a4 (capture)
Types in this puzzle
Hanging piece
A piece is left without protection — just take it.
A hanging piece is simply an unprotected piece you can take for free. It sounds primitive, yet most amateur games are decided exactly this way. Build the habit: before every move, sweep the board and note every undefended piece, yours and theirs. The classic mistake is hunting for a brilliant combination when all you need to do is bend down and pick up the gift.
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 #270.
SP-270 · BastionScout — King off-centre on c or f with a knight starting on the rim (a/h).
The king starts on c1, the rooks on b1 and h1, the queen on e1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
The bishops stand on f1 and g1; their long diagonals reach a6 and a7 once the e- and f-pawns step aside.
One second-rank pawn starts with no defender at all: a2.
The setup belongs to the BastionScout family; read right to left it becomes position 596.
The engine's main line opens with f3.
Morozov Balance Index: 93 of 100 — class A — most balanced. Engine evaluation of the starting position: +11 centipawns for White (depth 48, 400 000 000 nodes).
Explore position #270Provenance
Mined from the project's engine self-play games.
Verified by Stockfish at depth 20+.
Solution forcedness confirmed (verified).
Pack 002 · SP-270
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