Winning blow: rook to a5 (b5)
c9-27836naming 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 1420 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 b3, rook b5 f7, bishop h1, pawn b2 a4 c4 e4 d5 h5.
Black: king a7, queen a6, rook e5 g8, knight h4, pawn g4 a5 c5 d6 h6 b7.
11 white and 11 black pieces are on the board; the puzzle position arises after move 29.
The position in numbers
Material is level — 28 points of pieces on each side (pawn = 1, knight and bishop = 3, rook = 5, queen = 9).
The white king stands on b1, the black king on a7.
It is White to move on move 29, with 35 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 6. Files fully open (no pawns of either colour): f — natural highways for the rooks and queen. Half-open for White: g.
The White king has 4 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
29. Rxa5 Kb8 30. Rxa6
Why it works
- Best move. rook to a5 is exactly what the engine plays (#4).
- Well found: rook to a6 (#3).
- You win a piece — the queen.
- If instead Kb8, then Rxa6 and you win the queen.
Move by move
- 29. Rxa5 — rook to a5 (capture)
- Kb8 — king to b8
- 30. Rxa6 — rook to a6 (capture)
Types in this puzzle
Absolute pin
A piece is pinned against its king — it cannot legally move.
An absolute pin freezes a piece on the line between its own king and your long-range attacker: moving it is simply illegal. The pattern is three units on one straight line — your bishop, rook or queen, an enemy piece, and the enemy king behind it. A pinned piece neither attacks nor defends anything: treat it as if it were off the board. Pile up on it, ideally with a pawn, because running away is against the rules.
About this position
These pieces come from starting position #891.
SP-891 · BastionGuard — King shifted to c or f, knights kept clear of the edges — 168 positions in all.
The king starts on c1, the rooks on a1 and d1, the queen on b1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
A bishop starts in the corner on h1: it has a single diagonal, which the g-pawn unlocks, running out to a8.
Every pawn on the second rank is defended from the very first move.
The setup belongs to the BastionGuard family; read right to left it becomes position 65.
The engine's main line opens with g3.
Morozov Balance Index: 2 of 100 — class D — largest edge. Engine evaluation of the starting position: +53 centipawns for White (depth 41, 400 000 000 nodes).
Explore position #891Provenance
Mined from the project's engine self-play games.
Pack 010 · SP-891
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