Winning blow: bishop to a4 (c2·5)
c9-16130naming 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 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.
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 c1, rook b1 f1, bishop a1 c2, knight d3, pawn e2 g2 h2 f3 b4 d4 c5.
Black: king g8, queen c8, rook b5 f8, bishop d8, knight c6 f6, pawn a5 d6 e6 h6 c7 f7 g7.
14 white and 14 black pieces are on the board; the puzzle position arises after move 15.
The position in numbers
Material is level — 35 points of pieces on each side (pawn = 1, knight and bishop = 3, rook = 5, queen = 9).
The white king stands on g1, 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 7 pawns, Black 7. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: a.
White hold the bishop pair, an edge in open lines. The White king has 2 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
15. Ba4 Qb7 16. Bxb5
Why it works
- Great move! bishop to a4 keeps the pressure (+3.2).
- Spot on — bishop to b5 (+3.5).
- You win a piece — the rook.
- If instead Qb7, then Bxb5 and you win the rook.
Move by move
- 15. Ba4 — bishop to a4
- Qb7 — queen to b7
- 16. Bxb5 — bishop to b5 (capture)
Types in this puzzle
Quiet move
No check, no capture — yet this modest move decides the game.
A quiet move gives no check and takes nothing — yet it decides the game by creating an unstoppable threat or stealing the king's last square. This is the hardest class of moves: the eye hunts for loud blows while a modest shift does the winning. The clue: every forcing try runs into a defense, so seek the move that strengthens the threat or takes squares away. Train yourself to ask: what if I neither capture nor check, but quietly improve?
About this position
These pieces come from starting position #497.
SP-497 · BastionGuard — Off-centre king (c/f), no knight on the a- or h-file.
The king starts on f1, the rooks on b1 and h1, the queen on c1.
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.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
One second-rank pawn starts with no defender at all: a2.
The setup belongs to the BastionGuard family; read right to left it becomes position 555.
The engine's main line opens with c4.
Morozov Balance Index: 98 of 100 — class A — most balanced. Engine evaluation of the starting position: 0 centipawns for White (depth 46, 400 000 000 nodes).
In 50 self-play games White scored 48.0% (95% CI 34.8–61.5%).
Explore position #497Provenance
Mined from the project's engine self-play games.
Pack 007 · SP-497
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