Attack on the uncastled king: bishop to a4 (c2·5)
c9-24790naming 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.
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
Winning tactic: there is a move that gains a decisive advantage — find it.
Difficulty 1700 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.
An uncastled king in the centre is a standing target. Look for ways to open the central files and diagonals against it with checks and threats before it can shelter — every tempo the king spends in the middle is a chance for a combination.
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 a1, rook d1, bishop c2, knight d4, pawn a2 e2 f2 g2 g3.
Black: king e8, queen c5, rook f8, bishop c8, knight g6, pawn c4 a5 f5 e6 f7 h7.
10 white and 11 black pieces are on the board; the puzzle position arises after move 17.
The position in numbers
Black are ahead by 1 points of material (25 against 26; 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 e8.
It is White to move on move 17, with 32 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 5 pawns, Black 6. Files fully open (no pawns of either colour): b, d — natural highways for the rooks and queen. Half-open for White: c, h.
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. Ba4+ Bd7 18. Bxd7+ Kxd7 19. Nb3+ Qd5 20. Rxd5+
Why it works
- Great move! bishop to a4 keeps the pressure (+5.3).
- Well found: bishop to d7 (+5.3).
- Strong! knight to b3 is the sharp choice (+5.4).
- Best move. rook to d5 is exactly what the engine plays (+5.6).
- You win a piece — the queen.
- If instead Bd7, then Bxd7+ and you win the bishop.
Move by move
- 17. Ba4+ — bishop to a4 with check
- Bd7 — bishop to d7
- 18. Bxd7+ — bishop to d7 (capture) with check
- Kxd7 — king to d7 (capture)
- 19. Nb3+ — knight to b3 with check
- Qd5 — queen to d5
- 20. Rxd5+ — rook to d5 (capture) with check
Types in this puzzle
Win the pinned piece
The pinned piece cannot run — attack it again and win it.
A pinned piece cannot flee, which means you can win it outright by attacking it one more time. Count attackers against defenders: if you outnumber them, the piece is yours. The best extra attacker is a pawn, since it costs less than anything it might capture. Do not rush the capture — build up the pressure first, then harvest.
Uncastled king
The king lingered in the middle — punish the delay.
Punishing the uncastled king: your opponent delayed castling, and now his king is stuck on its starting square under fire. In Chess960 this is deadlier than in classical chess — the king may start in the center or near the edge, and the familiar defensive setups simply do not apply. The signs: the victim still holds castling rights, and the files toward his king are half-open. Open lines before the king manages to hide.
Discovered check
The moving piece opens a check — and is free to grab anything meanwhile.
With a discovered check the moving piece unmasks a check from the piece standing behind it. While the king deals with the check, the piece that moved grabs whatever it likes, free of charge. Look for your long-range piece on a line with the enemy king, with exactly one of your own pieces in between. The rule: among all the ways to step aside, pick the one that captures or attacks the most expensive loot.
About this position
These pieces come from starting position #868.
SP-868 · ThroneScout — A knight starts on the edge (a/h) and the king sits centrally on d or e; the mirror twin stays in this family too.
The king starts on e1, the rooks on d1 and f1, the queen on a1.
The kingside rook already stands on f1, so castling short moves only the king, from e1 to g1.
The bishops stand on b1 and c1; their long diagonals reach h7 and h6 once the c- and d-pawns step aside.
The second rank carries 2 pawns with no defender at all: g2, h2.
The setup belongs to the ThroneScout family; read right to left it becomes position 94.
The engine's main line opens with Ng3, bringing the knight out to g3.
Morozov Balance Index: 0 of 100 — class D — largest edge. Engine evaluation of the starting position: +75 centipawns for White (depth 43, 400 000 000 nodes).
In 50 self-play games White scored 59.0% (95% CI 45.2–71.5%).
Explore position #868Provenance
Mined from the project's engine self-play games.
Pack 013 · SP-868
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