Chess960 tactic on d6 (f5·3)
c9-09238naming 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 c1, queen h3, rook b1, bishop a1 h1, knight c5 f5, pawn c2 h2 g3.
Black: king c8, queen c4, rook b6, bishop a8 h8, knight f7 f8, pawn d4 b5 h5 a7 c7.
10 white and 12 black pieces are on the board; the puzzle position arises after move 25.
The position in numbers
Black are ahead by 2 points of material (29 against 31; 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 25, with 39 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 3 pawns, Black 5. Files fully open (no pawns of either colour): e, f — natural highways for the rooks and queen. Half-open for White: a, b, d.
The White king has 3 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
25. Nd6+ Kd8 26. Qh4+ Ng5 27. Qxg5+ Bf6 28. Qxf6#
Why it works
- Great move! knight to d6 keeps the pressure (#3).
- Well found: queen to h4 (#2).
- Strong! queen to g5 is the sharp choice (#1).
- Great move! queen to f6 keeps the pressure (#).
- The line ends in a forced mate in 4.
- If instead Kd8, then Qh4+ and you stay on top.
Move by move
- 25. Nd6+ — knight to d6 with check
- Kd8 — king to d8
- 26. Qh4+ — queen to h4 with check
- Ng5 — knight to g5
- 27. Qxg5+ — queen to g5 (capture) with check
- Bf6 — bishop to f6
- 28. Qxf6# — queen to f6 (capture) 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.
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.
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.
About this position
These pieces come from starting position #851.
SP-851 · BastionGuard — Off-centre king (c/f), no knight on the a- or h-file.
The king starts on c1, the rooks on b1 and e1, the queen on g1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
One second-rank pawn starts with no defender at all: a2.
The setup belongs to the BastionGuard family; read right to left it becomes position 99.
The engine's main line opens with e4, putting a pawn straight into the centre.
Morozov Balance Index: 80 of 100 — class A — most balanced. Engine evaluation of the starting position: +17 centipawns for White (depth 42, 400 000 000 nodes).
Explore position #851Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-851
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