Attack on the uncastled king: pawn to g7 (g6·4)
c9-10855naming 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.
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
Difficulty 2120 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.
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 e1, rook h1, bishop f6, knight f4, pawn a2 g2 b3 e5 g6.
Black: king f8, rook h8, bishop f5 b8, knight d1, pawn a6 b6 c6 h7.
9 white and 9 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 (16 against 18; 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 f8.
It is White to move on move 25, with 32 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 5 pawns, Black 4. Files fully open (no pawns of either colour): d, f — natural highways for the rooks and queen. Half-open for White: c, h.
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
25. g7+ Kf7 26. gxh8=Q c5 27. Qg7+ Ke8 28. Qe7#
Why it works
- Great move! pawn to g7 keeps the pressure (#3).
- Well found: pawn to h8 (#2).
- Precise: queen to g7 is the top choice (#1).
- Best move. queen to e7 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead Kf7, then gxh8=Q and you win the rook.
Move by move
- 25. g7+ — pawn to g7 with check
- Kf7 — king to f7
- 26. gxh8=Q — pawn to h8 (capture)
- c5 — pawn to c5
- 27. Qg7+ — queen to g7 with check
- Ke8 — king to e8
- 28. Qe7# — queen to e7 and it is checkmate
Types in this puzzle
Supported queen mate
The queen delivers mate face to face, protected by a friend.
The supported queen mate is the most common pattern of all: the queen lands next to the king and mates because a friendly piece or pawn protects her. The king is helpless — capturing is impossible, and the queen covers every neighboring square herself. Hunt for a protected square beside the enemy king: a knight, bishop or pawn eyeing it turns her invasion into mate. Verify one thing — that the square really is defended, or the king eats her.
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 #108.
SP-108 · BastionGuard — King off-centre on c or f with both knights on inner files.
The king starts on f1, the rooks on d1 and h1, the queen on a1.
The queenside rook already stands on d1, so castling long moves only the king, from f1 to c1.
The bishops stand on b1 and g1; their long diagonals reach h7 and a7 once the c- and f-pawns step aside.
Every pawn on the second rank is defended from the very first move.
The setup belongs to the BastionGuard family; read right to left it becomes position 860.
The engine's main line opens with d4, putting a pawn straight into the centre.
Morozov Balance Index: 89 of 100 — class A — most balanced. Engine evaluation of the starting position: +14 centipawns for White (depth 47, 400 000 000 nodes).
Explore position #108Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-108
Similar puzzles
In your browser or in the Android app. Nothing to install · Free, no ads