Attack on the uncastled king: bishop to b5 (a4·2)
c9-16629naming 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 1280 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.
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 h1, queen c1, rook a1 f6, bishop e3 a4, knight a3 g3, pawn b2 g2 h2.
Black: king e8, rook a8, bishop g8, knight h4 b5, pawn b4 d5 e5 b7 g7 h7.
11 white and 11 black pieces are on the board; the puzzle position arises after move 21.
The position in numbers
White are ahead by 14 points of material (34 against 20; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on h1, the black king on e8.
It is White to move on move 21, with 55 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 3 pawns, Black 6. Files fully open (no pawns of either colour): a, c, f — natural highways for the rooks and queen. Half-open for White: d, e.
White hold the bishop pair, an edge in open lines. The White king has 1 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
21. Bxb5+ Ke7 22. Qc5+ Kxf6 23. Rf1+
Why it works
- Best move. bishop to b5 is exactly what the engine plays (#4).
- Spot on — queen to c5 (#4).
- Precise: rook to f1 is the top choice (#3).
- You win decisive material (+15.0).
- If instead Ke7, then Bg5 and you win the knight.
Move by move
- 21. Bxb5+ — bishop to b5 (capture) with check
Types in this puzzle
Hanging piece
A piece is left without protection — just take it.
A hanging piece is simply an unprotected piece you can take for free. It sounds primitive, yet most amateur games are decided exactly this way. Build the habit: before every move, sweep the board and note every undefended piece, yours and theirs. The classic mistake is hunting for a brilliant combination when all you need to do is bend down and pick up the gift.
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.
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.
About this position
These pieces come from starting position #621.
SP-621 · ThroneScout — Centre-file king, rim knight: 204 of the 960 positions share this pattern.
The king starts on e1, the rooks on a1 and f1, the queen on c1.
The kingside rook already stands on f1, so castling short moves only the king, from e1 to g1.
The bishops stand on d1 and g1; their long diagonals reach h5 and a7 once the e- and f-pawns step aside.
One second-rank pawn starts with no defender at all: g2.
The setup belongs to the ThroneScout family; read right to left it becomes position 248.
The engine's main line opens with f4.
Morozov Balance Index: 18 of 100 — class D — largest edge. Engine evaluation of the starting position: +38 centipawns for White (depth 44, 400 000 000 nodes).
Explore position #621Provenance
Mined from the project's engine self-play games.
Pack 009 · SP-621
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