Winning blow: pawn to b5 (c4·5)
c9-25420naming 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 1200 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 f3, knight h1, pawn d3 c4 c7.
Black: king f8, rook a8, pawn h4 b5 f5 e7.
5 white and 6 black pieces are on the board; the puzzle position arises after move 37.
The position in numbers
Black are ahead by 3 points of material (6 against 9; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on f3, the black king on f8.
It is White to move on move 37, with 14 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 3 pawns, Black 4. Files fully open (no pawns of either colour): a, g — natural highways for the rooks and queen. Half-open for White: b, e, f, h.
The White king has 5 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
37. cxb5 Rc8 38. b6 Ke8 39. b7 Kd7 40. b8=Q
Why it works
- Great move! pawn to b5 keeps the pressure (+4.4).
- Well found: pawn to b6 (+4.8).
- Strong! pawn to b7 is the sharp choice (+5.0).
- Great move! pawn to b8 keeps the pressure (+5.2).
- You win a piece — the pawn.
- If instead Rc8, then b6 and you stay on top.
Move by move
- 37. cxb5 — pawn to b5 (capture)
- Rc8 — rook to c8
- 38. b6 — pawn to b6
- Ke8 — king to e8
- 39. b7 — pawn to b7
- Kd7 — king to d7
- 40. b8=Q — pawn to b8
Types in this puzzle
Promotion
The pawn reaches the last rank and becomes a queen — decisively.
Promotion turns a pawn on the last rank into a queen and rewrites the evaluation on the spot. In tactics the passer rarely walks in for free — usually a sacrifice clears its path. Count the tempi: how many moves does the pawn need, and can the defender stop it in time? And watch the promotion square itself — it must be out of enemy reach or won by force in your combination.
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.
Promotion race
Both sides push passers — win the race by a tempo.
A promotion race is a sprint between two passed pawns: both sides push toward the last rank, and victory goes to whoever queens first or queens with check. You will recognize it when both players have far-advanced passers that neither king can catch. Count the tempi literally, move by move, all the way to promotion. The classic mistake is spending a tempo on a "useful" move — in a race, almost any non-pawn move loses.
About this position
These pieces come from starting position #312.
SP-312 · BastionScout — King off-centre on c or f with a knight starting on the rim (a/h).
The king starts on f1, the rooks on d1 and g1, the queen on c1.
Castling short simply swaps the two pieces: the king on f1 and the rook on g1 trade places.
The bishops stand on b1 and e1; their long diagonals reach h7 and a5 once the c- and d-pawns step aside.
One second-rank pawn starts with no defender at all: h2.
The setup belongs to the BastionScout family; read right to left it becomes position 365.
The engine's main line opens with d4, putting a pawn straight into the centre.
Morozov Balance Index: 40 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +29 centipawns for White (depth 47, 400 000 000 nodes).
Explore position #312Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-312
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