Attack on the uncastled king: bishop to c6 (d7)
c9-09571naming 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.
Mate in 4: a forced checkmate in four moves — every reply is covered.
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 2400 ShuffleRating — expert level — few solve it at first try.
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.
A mate in four is a longer forced net: each of your moves is a check or an irresistible threat, and the king is driven step by step to a square where it is finally trapped. Verify that the defender has exactly one reply at every branch.
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 d1, queen e6, rook b1, bishop d7, knight a3, pawn a2 c2 h2 g3.
Black: king d8, rook a8, pawn b5 c5 a6.
9 white and 5 black pieces are on the board; the puzzle position arises after move 26.
The position in numbers
White are ahead by 16 points of material (24 against 8; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on d1, the black king on d8.
It is White to move on move 26, with 43 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 4 pawns, Black 3. Files fully open (no pawns of either colour): d, e, f — natural highways for the rooks and queen. Half-open for White: b.
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
26. Bc6 Ra7 27. Qe8+ Kc7 28. Qd7+ Kb8 29. Qd8#
Why it works
- Sensible development: bishop to c6.
- Spot on — queen to e8 (#2).
- Precise: queen to d7 is the top choice (#1).
- Best move. queen to d8 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead Ra7, then Qe8+ and you stay on top.
Move by move
- 26. Bc6 — bishop to c6
- Ra7 — rook to a7
- 27. Qe8+ — queen to e8 with check
- Kc7 — king to c7
- 28. Qd7+ — queen to d7 with check
- Kb8 — king to b8
- 29. Qd8# — queen to d8 and it is checkmate
Types in this puzzle
Mate in 4+
A long forced mating combination.
Mate in four or longer is a marathon of forcing moves where the grip must never loosen. The tools are the same: checks, double threats and sacrifices that deny the opponent a single free tempo. Do not juggle the whole tree at once — walk the main line all the way to mate first, then verify the side branches. If somewhere the defender finds one quiet move that holds, your very first move was wrong.
Absolute pin
A piece is pinned against its king — it cannot legally move.
An absolute pin freezes a piece on the line between its own king and your long-range attacker: moving it is simply illegal. The pattern is three units on one straight line — your bishop, rook or queen, an enemy piece, and the enemy king behind it. A pinned piece neither attacks nor defends anything: treat it as if it were off the board. Pile up on it, ideally with a pawn, because running away is against the rules.
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 #631.
SP-631 · ThroneGuard — A central king (d or e) and two knights tucked onto inner files: the family that holds the standard array, SP-518.
The king starts on d1, the rooks on a1 and f1, the queen on e1.
The kingside rook already stands on f1, so castling short moves only the king, from d1 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: h2.
The setup belongs to the ThroneGuard family; read right to left it becomes position 226.
The engine's main line opens with Nc3, bringing the knight out to c3.
Morozov Balance Index: 86 of 100 — class A — most balanced. Engine evaluation of the starting position: +15 centipawns for White (depth 48, 400 000 000 nodes).
Explore position #631Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-631
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