Attack on the uncastled king: queen to g8 (b3·5)
c9-26035naming 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 3: a forced sequence that ends in checkmate.
A fork made possible by the Chess960 piece placement.
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
Difficulty 1630 ShuffleRating — for advanced tacticians.
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.
In a mate in three every move must be forcing; the defender should never get a free tempo. Find the check or threat that herds the king, calculate the single defence to each, and confirm the net closes on the third move.
A set-up fork needs one preparing move before the fork lands — a check that drives the king onto the forking square, or a capture that lines the targets up. Find the preparation first, then the fork it makes possible.
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.
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 b3, rook d1, bishop g2 g5, knight d3, pawn b2 c2 h2 b5.
Black: king c8, rook a8, bishop g7, knight e4, pawn a5 f5 b7 c7 h7.
10 white and 9 black pieces are on the board; the puzzle position arises after move 23.
The position in numbers
White are ahead by 11 points of material (27 against 16; 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 23, with 40 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 4 pawns, Black 5. Files fully open (no pawns of either colour): d, e, g — natural highways for the rooks and queen. Half-open for White: a, f.
White hold the bishop pair, an edge in open lines. The White king has 1 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
23. Qg8+ Bf8 24. Qxf8+ Kd7 25. Nc5#
Why it works
- Best move. queen to g8 is exactly what the engine plays (#2).
- Spot on — queen to f8 (#1).
- Precise: knight to c5 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Bf8, then Qxf8+ and you win the bishop.
Move by move
- 23. Qg8+ — queen to g8 with check
- Bf8 — bishop to f8
- 24. Qxf8+ — queen to f8 (capture) with check
- Kd7 — king to d7
- 25. Nc5# — knight to c5 and it is checkmate
Types in this puzzle
Double-check mate
Double check leaves only king moves — and there are none.
The double-check mate ends the game with check from two pieces at once, leaving the king with nothing. Neither capturing nor blocking works against a double check — only a king move, and here there is none. Look for a discovered check where the front piece checks too: it may even land on a defended square with total impunity. That is why the double check crowns so many of the most beautiful sacrificial combinations.
Setup fork
The random setup allows a fork that classical chess never sees.
A setup fork is a double attack that exists only because of the unusual starting squares — in classical chess these targets never stand side by side. Look for pairs of undefended pieces on your opponent's back rank and for squares from which a knight or pawn hits both at once. Such forks usually appear within the first moves, before the pieces disperse. In every new position, note right away which starting pieces are defended by no one.
Mate in 3
A forced checkmate in three moves.
Mate in three is a forced staircase: each of your moves narrows the opponent's choices, and the third one ends the game. Look for the start among checks and sacrifices — quiet first moves are rare in mating problems, but deliciously sneaky. Keep the tree in your head: every defense gets its own branch. Do not stop calculating after move two — see the final mating picture with your own eyes.
About this position
These pieces come from starting position #670.
SP-670 · BastionGuard — Both knights begin inside the board while the king stands on c or f; a position and its mirror twin share this family.
The king starts on c1, the rooks on a1 and d1, the queen on h1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
The bishops stand on f1 and g1; their long diagonals reach a6 and a7 once the e- and f-pawns step aside.
The pawn on b2 is defended by the king alone — the same soft spot f2 is in the classical setup.
The setup belongs to the BastionGuard family; read right to left it becomes position 196.
The engine's main line opens with e4, putting a pawn straight into the centre.
Morozov Balance Index: 37 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +30 centipawns for White (depth 49, 400 000 000 nodes).
Explore position #670Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-670
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