Winning blow: pawn to b7 (c6·5)
c9-17374naming 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 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.
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 f1, queen b3, rook a1 g1, bishop e1 f3, knight e2, pawn a2 b2 c2 f2 g2 h3 e4 c6.
Black: king g8, queen c8, rook a8 f8, bishop f4 f7, knight g6, pawn a3 e5 d6 b7 c7 g7 h7.
15 white and 14 black pieces are on the board; the puzzle position arises after move 15.
The position in numbers
White are ahead by 1 points of material (36 against 35; 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 g8.
It is White to move on move 15, with 36 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 8 pawns, Black 7. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: 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
15. cxb7 axb2 16. Rb1 Qd7 17. bxa8=Q
Why it works
- Great move! pawn to b7 keeps the pressure (+3.4).
- rook to b1 develops smoothly.
- Precise: pawn to a8 is the top choice (+3.5).
- You win a piece — the rook.
- If instead axb2, then Rb1 and you stay on top.
Move by move
- 15. cxb7 — pawn to b7 (capture)
- axb2 — pawn to b2 (capture)
- 16. Rb1 — rook to b1
- Qd7 — queen to d7
- 17. bxa8=Q — pawn to a8 (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.
Pawn fork
A humble pawn steps forward and attacks two pieces at once.
A pawn fork is a single pawn step that attacks two pieces at once. Since the pawn is the cheapest unit on the board, the trade is always a bargain — the opponent saves only one of the two targets. The pattern: two enemy pieces on the same rank, one file apart, with a square for your pawn between them. Before parking your pieces near enemy pawns, always ask whether one little push forks them both.
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.
About this position
These pieces come from starting position #617.
SP-617 · 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 a1 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 d1 and e1; their long diagonals reach h5 and a5 once the e- 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 249.
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 48, 400 000 000 nodes).
Explore position #617Provenance
Mined from the project's engine self-play games.
Pack 006 · SP-617
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