Chess960 tactic on f6 (d4·3)
c9-10236naming 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: a forcing sequence that ends the game — the king has no escape.
Mate in 4: a forced checkmate in four moves — every reply is covered.
A fork made possible by the Chess960 piece placement.
Difficulty 2350 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.
This is a forced mating attack. Start from the enemy king: which of its squares are already covered, and which move takes away the rest while keeping the king in check? Forcing moves — checks and captures — are what turn an attack into mate.
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.
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.
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 d4, rook f2, bishop b1 b2, pawn a2 d2 e2 h2 b3 g6.
Black: king g7, queen a8, rook d8, bishop g3 h5, knight f6 h8, pawn d5 a6 b7 h7.
11 white and 11 black pieces are on the board; the puzzle position arises after move 21.
The position in numbers
Black are ahead by 4 points of material (26 against 30; 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 g7.
It is White to move on move 21, with 36 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 4. Files fully open (no pawns of either colour): c, f — natural highways for the rooks and queen.
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
21. Qxf6+ Kh6 22. Qg7+ Kg5 23. Bf6+ Kg4 24. Bf5#
Why it works
- Best move. queen to f6 is exactly what the engine plays (#3).
- Spot on — queen to g7 (#2).
- Precise: bishop to f6 is the top choice (#1).
- Best move. bishop to f5 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead Kh6, then Qg7+ and you win the knight.
Move by move
- 21. Qxf6+ — queen to f6 (capture) with check
- Kh6 — king to h6
- 22. Qg7+ — queen to g7 with check
- Kg5 — king to g5
- 23. Bf6+ — bishop to f6 with check
- Kg4 — king to g4
- 24. Bf5# — bishop to f5 and it is checkmate
Types in this puzzle
Boden's mate
Two bishops cross their diagonals over a king blocked by its own pieces.
Boden's mate crosses two bishop diagonals over a king blocked by its own pieces. The classic victim has castled on the queenside: its own rook and pawns have stolen the escape squares, and the bishops slash crosswise. The trigger is usually a queen sacrifice that blasts open the second diagonal. Whenever the enemy king is boxed in by its friends, ask whether both of your bishops can reach it on crossing diagonals.
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 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.
About this position
These pieces come from starting position #868.
SP-868 · ThroneScout — A knight starts on the edge (a/h) and the king sits centrally on d or e; the mirror twin stays in this family too.
The king starts on e1, the rooks on d1 and f1, the queen on a1.
The kingside rook already stands on f1, so castling short moves only the king, from e1 to g1.
The bishops stand on b1 and c1; their long diagonals reach h7 and h6 once the c- and d-pawns step aside.
The second rank carries 2 pawns with no defender at all: g2, h2.
The setup belongs to the ThroneScout family; read right to left it becomes position 94.
The engine's main line opens with Ng3, bringing the knight out to g3.
Morozov Balance Index: 0 of 100 — class D — largest edge. Engine evaluation of the starting position: +75 centipawns for White (depth 43, 400 000 000 nodes).
In 50 self-play games White scored 59.0% (95% CI 45.2–71.5%).
Explore position #868Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-868
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