Attack on the uncastled king: rook to b8 (b1·18)
c9-21911naming 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 e1, queen a6, rook b1, bishop h1, pawn a2 d2 e2 h2 g3 f4.
Black: king e8, rook b8 f8, bishop a1 g8, knight a7 d8, pawn c4 e4 f5 d6 g6 h7.
10 white and 13 black pieces are on the board; the puzzle position arises after move 16.
The position in numbers
Black are ahead by 5 points of material (23 against 28; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on e1, the black king on e8.
It is White to move on move 16, with 36 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 6. Files fully open (no pawns of either colour): b — natural highways for the rooks and queen. Half-open for White: c.
Black hold the bishop pair, an edge in open lines. The White king has 4 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
16. Rxb8 Rf7 17. Ra8 c3 18. Qa4+ Rd7 19. Rxa7
Why it works
- Great move! rook to b8 keeps the pressure (+4.3).
- rook to a8 develops smoothly.
- Precise: queen to a4 is the top choice (+4.4).
- Best move. rook to a7 is exactly what the engine plays (+4.4).
- You win a piece — the rook.
- If instead Rf7, then Ra8 and you win the rook.
Move by move
- 16. Rxb8 — rook to b8 (capture)
- Rf7 — rook to f7
- 17. Ra8 — rook to a8
- c3 — pawn to c3
- 18. Qa4+ — queen to a4 with check
- Rd7 — rook to d7
- 19. Rxa7 — rook to a7 (capture)
Types in this puzzle
Royal fork
A fork with check: the king must move, and the second piece is lost.
A royal fork is a fork with check — one of the two targets is the king itself. The check must be answered first, so nobody is left to rescue the second piece. Look for squares where your piece gives check and simultaneously attacks an undefended queen or rook. It is the most reliable fork of all, because your opponent literally has no choice.
Only move
Everything else loses — find the only move that holds.
An only move is a position where everything loses except one single continuation. You cannot play "by hand" here: run through fundamentally different defenses — run away, block, trade, counterattack — and discard the ones that fail. The hallmark of these puzzles is that the obvious moves lose quickly while the solution often looks strange. First understand exactly what the threat is — then the one saving move reveals itself.
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 #143.
SP-143 · ThroneScout — King in the middle of the rank, with a knight already committed to the corner.
The king starts on e1, the rooks on b1 and f1, the queen on c1.
The kingside rook already stands on f1, so castling short moves only the king, from e1 to g1.
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 ThroneScout family; read right to left it becomes position 816.
The engine's main line opens with f4.
Morozov Balance Index: 78 of 100 — class A — most balanced. Engine evaluation of the starting position: +18 centipawns for White (depth 48, 400 000 000 nodes).
Explore position #143Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-143
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