Winning blow: rook to a1 (b1·3)
c9-17134naming 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 g1, queen b3, rook b1, knight e3 d4, pawn c2 e2 f2 h2 g3 d5.
Black: king g8, queen b7, rook a1 f8, knight b6 e8, pawn b5 d6 g6 f7 h7.
11 white and 11 black pieces are on the board; the puzzle position arises after move 20.
The position in numbers
Black are ahead by 4 points of material (26 against 30; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on g1, the black king on g8.
It is White to move on move 20, with 35 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 5. Files fully open (no pawns of either colour): a — natural highways for the rooks and queen. Half-open for White: b.
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
20. Rxa1 Nc7 21. Nxb5 Nbxd5 22. Nxd5 Nxd5 23. Nxd6
Why it works
- Great move! rook to a1 keeps the pressure (+3.1).
- Spot on — knight to b5 (+3.0).
- Precise: knight to d5 is the top choice (+3.1).
- Best move. knight to d6 is exactly what the engine plays (+2.6).
- You win a piece — the rook.
- If instead Nc7, then Nxb5 and you win the rook.
Move by move
- 20. Rxa1 — rook to a1 (capture)
- Nc7 — knight to c7
- 21. Nxb5 — knight to b5 (capture)
- Nbxd5 — knight to d5 (capture)
- 22. Nxd5 — knight to d5 (capture)
- Nxd5 — knight to d5 (capture)
- 23. Nxd6 — knight to d6 (capture)
Types in this puzzle
Discovered attack
A piece steps aside and opens a second attack from the piece behind it.
A discovered attack works like a curtain: one piece steps off the line and unveils the long-range piece behind it. The beauty is that the moving piece can create a second threat of its own — two attacks in one move. Look for your stacked pairs: a bishop or rook behind a knight or pawn, aimed through them at something valuable. Send the front piece to the most aggressive square — a discovery without a second threat wastes half its power.
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.
Winning exchange
A forced series of captures on one square ends in your favour.
A winning exchange is a forced series of captures on one square that leaves you ahead in material. It is pure arithmetic: count the attackers and defenders of the square and note the value of every piece in the queue. Capture in the right order — cheap pieces first, expensive ones later — or a winning trade turns into a losing one. The classic error is stopping the count halfway and missing the opponent's final recapture.
About this position
These pieces come from starting position #403.
SP-403 · BastionGuard — The king starts one file off-centre, on c or f, with neither knight in a corner.
The king starts on f1, the rooks on b1 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 BastionGuard family; read right to left it becomes position 739.
The engine's main line opens with g3.
Morozov Balance Index: 83 of 100 — class A — most balanced. Engine evaluation of the starting position: +16 centipawns for White (depth 45, 400 000 000 nodes).
Explore position #403Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-403
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