Winning blow: pawn to b7 (c6·4)
c9-15430naming 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 1060 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 f1, rook f2 a8, pawn a2 g3 h4 c6.
Black: king e7, rook h6, bishop b7, knight d4, pawn e4 a7 d7 f7 h7.
7 white and 9 black pieces are on the board; the puzzle position arises after move 37.
The position in numbers
Black are ahead by 2 points of material (14 against 16; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on f1, the black king on e7.
It is White to move on move 37, with 29 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 4 pawns, Black 5. Files fully open (no pawns of either colour): b — natural highways for the rooks and queen. Half-open for White: d, e, f.
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
37. cxb7 Rb6 38. b8=R Rxb8 39. Rxb8
Why it works
- Great move! pawn to b7 keeps the pressure (+5.1).
- pawn to b8 develops smoothly.
- Strong! rook to b8 is the sharp choice (+5.6).
- You win a piece — the rook.
- If instead Rb6, then b8=R and you win the bishop.
Move by move
- 37. cxb7 — pawn to b7 (capture)
- Rb6 — rook to b6
- 38. b8=R — pawn to b8
- Rxb8 — rook to b8 (capture)
- 39. Rxb8 — rook to b8 (capture)
Types in this puzzle
Underpromotion
Promoting to a knight or rook — not a queen — is the only way to win.
Underpromotion means choosing a knight, rook or bishop instead of a queen — and winning precisely because of it. The usual hero is the knight, which delivers a check or a fork from the promotion square in a way no queen can. A rook is chosen when a fresh queen would produce stalemate. When your pawn reaches the last rank, never promote on autopilot — first ask what the knight can do.
Endgame tactic
Tactics live in the endgame too — strike while material is scarce.
Tactics do not retire when the queens come off: forks, pins and double attacks live on in the endgame. With so little material left, every tactical loss is almost always decisive. The signs are the usual ones — undefended pieces, king and piece on one line, a pawn about to promote. Even in a "technical" ending, scan for a shot before every move, both yours and your opponent's.
Counter-strike
Don't defend — answer the threat with a bigger one.
The counter-strike: instead of defending against the threat, you answer with a bigger threat of your own. While your opponent grabs a pawn, you deliver mate — the arithmetic favors you. Look for a counter when direct defenses fail: do you have a check, an attack on the queen, a mating threat? The beginner's error is meeting every threat with a reflexive defense without checking the counterattacking resources first.
About this position
These pieces come from starting position #305.
SP-305 · BastionScout — King shifted to c or f, with a knight committed to the corner from move one.
The king starts on f1, the rooks on e1 and g1, the queen on c1.
Castling short simply swaps the two pieces: the king on f1 and the rook on g1 trade places.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
The second rank carries 2 pawns with no defender at all: a2, h2.
The setup belongs to the BastionScout family; read right to left it becomes position 363.
The engine's main line opens with b4.
Morozov Balance Index: 31 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +32 centipawns for White (depth 42, 400 000 000 nodes).
Explore position #305Provenance
Mined from the project's engine self-play games.
Pack 006 · SP-305
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