Attack on the uncastled king: knight to b5 (a3·4)
c9-04138naming 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 780 ShuffleRating — for beginners taking their first steps in Chess960 tactics.
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 b1, queen c4, rook d1 h1, bishop f1 e3, knight a3, pawn a2 b2 d2 g3 e4 f4 h4.
Black: king c8, queen b8, rook a8 h8, bishop e7, knight d4 b5, pawn a5 c5 e5 f6 d7 g7 h7.
14 white and 14 black pieces are on the board; the puzzle position arises after move 16.
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 b1, the black king on c8.
It is White to move on move 16, with 38 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: c.
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
16. Nxb5 Nxb5 17. Qxb5 Qa7 18. Qc4
Why it works
- Great move! knight to b5 keeps the pressure (+4.9).
- Well found: queen to b5 (+5.4).
- A natural move: queen to c4.
- You win a piece — the knight.
- If instead a4, then Bxd4 and you win the knight.
Move by move
- 16. Nxb5 — knight to b5 (capture)
Types in this puzzle
Winning blow
Find the strike that wins material by force.
A winning blow is a forced material gain that does not fit a single textbook motif. The general tactical recipe applies: spot loose pieces, an awkwardly placed king, overloaded lines. Go through the forcing moves in order of violence — checks, captures, threats — because most combinations start with one of them. Do not judge by feel: calculate the concrete line until the outcome is beyond doubt.
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.
About this position
These pieces come from starting position #702.
SP-702 · BastionGuard — King off-centre on c or f with both knights on inner files.
The king starts on c1, the rooks on a1 and h1, the queen on b1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
The bishops stand on f1 and g1; their long diagonals reach a6 and a7 once the e- and f-pawns step aside.
The pawn on d2 is defended by the king alone — the same soft spot f2 is in the classical setup.
The setup belongs to the BastionGuard family; read right to left it becomes position 452.
The engine's main line opens with e4, putting a pawn straight into the centre.
Morozov Balance Index: 40 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +29 centipawns for White (depth 42, 400 000 000 nodes).
Explore position #702Provenance
Mined from the project's engine self-play games.
Verified by Stockfish at depth 20+.
Solution forcedness confirmed (verified).
Pack 002 · SP-702
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