Winning blow: king to a2 (b1·23)
c9-10599naming 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.
Winning tactic: there is a move that gains a decisive advantage — find it.
Difficulty 1250 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.
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 b1, queen c3, rook b3 f5, bishop c2, knight d4, pawn b2 e2 g2 h7.
Black: king h8, queen h1, rook b7 e8, bishop f7, knight e5, pawn a5 d5 c6.
10 white and 9 black pieces are on the board; the puzzle position arises after move 35.
The position in numbers
White are ahead by 1 points of material (29 against 28; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on b1, the black king on h8.
It is White to move on move 35, with 4 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 4 pawns, Black 3. Files fully open (no pawns of either colour): f — natural highways for the rooks and queen. Half-open for White: a, c, d.
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
35. Ka2 Rxb3 36. Nxb3 d4 37. Qxd4
Why it works
- Great move! king to a2 keeps the pressure (+3.8).
- Spot on — knight to b3 (+3.5).
- Strong! queen to d4 is the sharp choice (+4.0).
- You reach a winning position (+4.0).
- If instead Rxb3, then Nxb3 and you stay on top.
Move by move
- 35. Ka2 — king to a2
- Rxb3 — rook to b3 (capture)
- 36. Nxb3 — knight to b3 (capture)
- d4 — pawn to d4
- 37. Qxd4 — queen to d4 (capture)
Types in this puzzle
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.
Only move
Everything else loses — find the only move that holds.
An only move is a position where everything loses except one single continuation. You cannot play "by hand" here: run through fundamentally different defenses — run away, block, trade, counterattack — and discard the ones that fail. The hallmark of these puzzles is that the obvious moves lose quickly while the solution often looks strange. First understand exactly what the threat is — then the one saving move reveals itself.
About this position
These pieces come from starting position #557.
SP-557 · BastionGuard — Off-centre king (c/f), no knight on the a- or h-file.
The king starts on c1, the rooks on a1 and h1, the queen on f1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
The bishops stand on d1 and g1; their long diagonals reach h5 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 504.
The engine's main line opens with e4, putting a pawn straight into the centre.
Morozov Balance Index: 0 of 100 — class D — largest edge. Engine evaluation of the starting position: +63 centipawns for White (depth 44, 400 000 000 nodes).
In 50 self-play games White scored 65.0% (95% CI 51.1–76.7%).
Explore position #557Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-557
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