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Winning blow: pawn to b5 (b4)

Shuffle Rating 1110Theme: Chess960 twist: use the unusual starting setup of the pieces.
White to move — find the best continuation

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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 1110 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 e1, queen e2, rook g1, bishop c1 c2, pawn f2 e3 g3 b4.

Black: king e8, queen c6, rook a6, bishop c7, knight f8, pawn c3 a7 b7 e7 f7.

9 white and 10 black pieces are on the board; the puzzle position arises after move 22.

The position in numbers

Black are ahead by 1 points of material (24 against 25; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.

The white king stands on e1, the black king on e8.

It is White to move on move 22, with 33 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): d, h — natural highways for the rooks and queen. Half-open for White: a, c.

White hold the bishop pair, an edge in open lines. 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

22. b5 Ra1 23. bxc6

Why it works

  • Great move! pawn to b5 keeps the pressure (+4.3).
  • Well found: pawn to c6 (+3.9).
  • You win a piece — the queen.
  • If instead Ra1, then bxc6 and you win the queen.

Move by move

  • 22. b5 — pawn to b5
  • Ra1 — rook to a1
  • 23. bxc6 — pawn to c6 (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.

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.

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.

About this position

These pieces come from starting position #276.

SP-276 · ThroneScout — King on a central file (d/e) with a knight starting on the rim (a/h).

The king starts on e1, the rooks on d1 and g1, the queen on h1.

The queenside rook already stands on d1, so castling long moves only the king, from e1 to c1.

The bishops stand on b1 and c1; their long diagonals reach h7 and h6 once the c- and d-pawns step aside.

The pawn on e2, f2 is defended by the king alone — the same soft spot f2 is in the classical setup.

The setup belongs to the ThroneScout family; read right to left it becomes position 590.

The engine's main line opens with d4, putting a pawn straight into the centre.

Morozov Balance Index: 47 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +27 centipawns for White (depth 45, 400 000 000 nodes).

Explore position #276

Provenance

Mined from the project's engine self-play games.

Pack 007 · SP-276

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