Winning blow: pawn to a3 (b2·6)
c9-21318naming 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, rook a1, bishop e1 e4, knight e2, pawn a2 b2 g2 h2 e3 e6.
Black: king f8, queen a3, rook a8, bishop b8, knight d5 c8, pawn e5 a7 b7 g7 h7.
11 white and 11 black pieces are on the board; the puzzle position arises after move 17.
The position in numbers
Black are ahead by 8 points of material (20 against 28; 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 f8.
It is White to move on move 17, with 34 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): c, d, f — natural highways for the rooks and queen.
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
17. bxa3 Ncb6 18. Rd1 Bd6 19. Bxd5 Nxd5 20. Rxd5
Why it works
- Great move! pawn to a3 keeps the pressure (+4.6).
- rook to d1 develops smoothly.
- Precise: bishop to d5 is the top choice (+4.8).
- Best move. rook to d5 is exactly what the engine plays (+4.9).
- You win a piece — the queen.
- If instead Ncb6, then Rd1 and you win the queen.
Move by move
- 17. bxa3 — pawn to a3 (capture)
- Ncb6 — knight to b6
- 18. Rd1 — rook to d1
- Bd6 — bishop to d6
- 19. Bxd5 — bishop to d5 (capture)
- Nxd5 — knight to d5 (capture)
- 20. Rxd5 — rook to d5 (capture)
Types in this puzzle
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.
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.
About this position
These pieces come from starting position #520.
SP-520 · BastionGuard — Both knights begin inside the board while the king stands on c or f; a position and its mirror twin share this family.
The king starts on f1, the rooks on a1 and h1, the queen on d1.
Castling ends where it always does: king to g1 and rook to f1 on the short side, king to c1 and rook to d1 on the long one.
The bishops stand on b1 and e1; their long diagonals reach h7 and a5 once the c- and d-pawns step aside.
One second-rank pawn starts with no defender at all: b2.
The setup belongs to the BastionGuard family; read right to left it becomes position 541.
The engine's main line opens with e4, putting a pawn straight into the centre.
Morozov Balance Index: 75 of 100 — class B — balanced. Engine evaluation of the starting position: +19 centipawns for White (depth 44, 400 000 000 nodes).
Explore position #520Provenance
Mined from the project's engine self-play games.
Pack 008 · SP-520
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