Winning blow: pawn to a8 (b7)
c9-17942naming 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 1870 ShuffleRating — for advanced tacticians.
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 c1, queen b3, rook b1 e1, bishop h1 f2, knight d2 c6, pawn a2 e3 d4 f4 h4 b7.
Black: king c7, queen e7, rook a8 e8, bishop f7 h8, knight f6, pawn g4 d5 e6 g6 h6 a7.
14 white and 13 black pieces are on the board; the puzzle position arises after move 20.
The position in numbers
White are ahead by 3 points of material (37 against 34; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on c1, the black king on c7.
It is White to move on move 20, with 53 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): c — natural highways for the rooks and queen. Half-open for White: g.
The White king has 5 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
20. bxa8=N+ Kd6 21. Qa3+ Kd7 22. Ne5+
Why it works
- Best move. pawn to a8 is exactly what the engine plays (#4).
- Spot on — queen to a3 (#3).
- Precise: knight to e5 is the top choice (#3).
- You win a piece — the rook.
- If instead Kd6, then Nc4+ and you win the rook.
Move by move
- 20. bxa8=N+ — pawn to a8 (capture) with check
Types in this puzzle
Underpromotion
Promoting to a knight or rook — not a queen — is the only way to win.
Underpromotion means choosing a knight, rook or bishop instead of a queen — and winning precisely because of it. The usual hero is the knight, which delivers a check or a fork from the promotion square in a way no queen can. A rook is chosen when a fresh queen would produce stalemate. When your pawn reaches the last rank, never promote on autopilot — first ask what the knight can do.
Counter-strike
Don't defend — answer the threat with a bigger one.
The counter-strike: instead of defending against the threat, you answer with a bigger threat of your own. While your opponent grabs a pawn, you deliver mate — the arithmetic favors you. Look for a counter when direct defenses fail: do you have a check, an attack on the queen, a mating threat? The beginner's error is meeting every threat with a reflexive defense without checking the counterattacking resources first.
About this position
These pieces come from starting position #351.
SP-351 · BastionScout — Off-centre king plus a rim knight (a/h): 168 positions carry this shape.
The king starts on c1, the rooks on b1 and e1, the queen on d1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
A bishop starts in the corner on h1: it has a single diagonal, which the g-pawn unlocks, running out to a8.
One second-rank pawn starts with no defender at all: a2.
The setup belongs to the BastionScout family; read right to left it becomes position 320.
The engine's main line opens with f4.
Morozov Balance Index: 83 of 100 — class A — most balanced. Engine evaluation of the starting position: +16 centipawns for White (depth 42, 400 000 000 nodes).
Explore position #351Provenance
Mined from the project's engine self-play games.
Pack 014 · SP-351
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