Attack on the uncastled king: knight to a5 (b3·23)
c9-26155naming 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 1250 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 c1, queen a6, rook b1 f1, bishop g1, knight d1 b3, pawn a2 b2 e2 h2 d3 g3 c4 f4.
Black: king c8, queen c7, rook b7 f8, bishop f7 h8, knight b6, pawn c5 f5 d6 g6 a7 e7 h7.
15 white and 14 black pieces are on the board; the puzzle position arises after move 13.
The position in numbers
White are ahead by 1 points of material (36 against 35; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on c1, the black king on c8.
It is White to move on move 13, with 33 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.
Black hold the bishop pair, an edge in open lines. 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
13. Na5 Rd8 14. Qxb7+ Qxb7 15. Nxb7
Why it works
- Great move! knight to a5 keeps the pressure (+4.0).
- Spot on — queen to b7 (+3.9).
- Strong! knight to b7 is the sharp choice (+4.0).
- You win a piece — the queen.
- If instead Rd8, then Qxb7+ and you win the rook.
Move by move
- 13. Na5 — knight to a5
- Rd8 — rook to d8
- 14. Qxb7+ — queen to b7 (capture) with check
- Qxb7 — queen to b7 (capture)
- 15. Nxb7 — knight to b7 (capture)
Types in this puzzle
Win the pinned piece
The pinned piece cannot run — attack it again and win it.
A pinned piece cannot flee, which means you can win it outright by attacking it one more time. Count attackers against defenders: if you outnumber them, the piece is yours. The best extra attacker is a pawn, since it costs less than anything it might capture. Do not rush the capture — build up the pressure first, then harvest.
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.
Trapped piece
The attacked piece has no safe square — it is caught.
Trapping a piece means the attacked piece has no safe square left — it simply perishes. Do not chase it around; build a cage instead: cut off the escape squares with pawns and pieces first, and attack last. The typical victim has wandered deep into your camp or is stuck at the edge of the board, where its mobility is tiny. And always check the way home for your own raiders — or the trapped piece will be yours.
About this position
These pieces come from starting position #271.
SP-271 · BastionScout — A c- or f-file king with at least one knight out on the edge.
The king starts on c1, the rooks on b1 and f1, the queen on e1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
A bishop starts in the corner on h1: it has a single diagonal, which the g-pawn unlocks, running out to a8.
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 592.
The engine's main line opens with f4.
Morozov Balance Index: 10 of 100 — class D — largest edge. Engine evaluation of the starting position: +43 centipawns for White (depth 47, 400 000 000 nodes).
Explore position #271Provenance
Mined from the project's engine self-play games.
Pack 009 · SP-271
Similar puzzles
In your browser or in the Android app. Nothing to install · Free, no ads