Winning blow: queen to a3 (b2)
c9-16208naming 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.
A fork made possible by the Chess960 piece placement.
Winning tactic: there is a move that gains a decisive advantage — find it.
Difficulty 1430 ShuffleRating — club-player level.
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 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.
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 a2, queen b2, rook f1, bishop g1 e4, knight h5, pawn g2 h2 b3 f5 e6.
Black: king e7, queen a6, rook c7 f8, knight h4, pawn g5 f6 a7 b7 h7.
11 white and 10 black pieces are on the board; the puzzle position arises after move 27.
The position in numbers
White are ahead by 1 points of material (28 against 27; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on a2, the black king on e7.
It is White to move on move 27, with 2 legal replies to weigh — only the line that keeps the advantage solves the puzzle. White are in check right now, so every reply must answer the check.
White keeps 5 pawns, Black 5. Files fully open (no pawns of either colour): c, d — natural highways for the rooks and queen. Half-open for White: a.
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
27. Qa3+ Qxa3+ 28. Kxa3 Rd8 29. g3 Nxf5 30. Bxf5
Why it works
- Great move! queen to a3 keeps the pressure (+4.7).
- Well found: king to a3 (+5.0).
- A natural move: pawn to g3.
- Best move. bishop to f5 is exactly what the engine plays (+5.0).
- You win decisive material (+5.0).
- If instead Qxa3+, then Kxa3 and you stay on top.
Move by move
- 27. Qa3+ — queen to a3 with check
- Qxa3+ — queen to a3 (capture) with check
- 28. Kxa3 — king to a3 (capture)
- Rd8 — rook to d8
- 29. g3 — pawn to g3
- Nxf5 — knight to f5 (capture)
- 30. Bxf5 — bishop to f5 (capture)
Types in this puzzle
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.
Winning blow
Find the strike that wins material by force.
A winning blow is a forced material gain that does not fit a single textbook motif. The general tactical recipe applies: spot loose pieces, an awkwardly placed king, overloaded lines. Go through the forcing moves in order of violence — checks, captures, threats — because most combinations start with one of them. Do not judge by feel: calculate the concrete line until the outcome is beyond doubt.
Blocking save
Block the check with tempo — and turn the game around.
The blocking save: you interpose a piece against the check — not passively, but with tempo, so the blocker creates a threat of its own. Such a block turns defense into attack. Whenever you are checked, compare all three replies — capture, move the king, interpose — and among the interpositions hunt for the one that counterattacks. The mistake is automatically stepping aside with the king when an active block would have turned the game around.
About this position
These pieces come from starting position #604.
SP-604 · 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 a1 and f1, the queen on c1.
The kingside rook already stands on f1, so castling short moves only the king, from e1 to g1.
The bishops stand on b1 and g1; their long diagonals reach h7 and a7 once the c- and f-pawns step aside.
One second-rank pawn starts with no defender at all: g2.
The setup belongs to the ThroneScout family; read right to left it becomes position 268.
The engine's main line opens with f4.
Morozov Balance Index: 0 of 100 — class D — largest edge. Engine evaluation of the starting position: +81 centipawns for White (depth 45, 400 000 000 nodes).
In 50 self-play games White scored 63.0% (95% CI 49.1–75.0%).
Explore position #604Provenance
Mined from the project's engine self-play games.
Pack 010 · SP-604
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