Castling-960 to the rescue on a1 (d1·11)
c9-19504naming tag (square·N)Opens in the app if installed, otherwise downloads the APK.
The tactical motive
Castling 960: the strongest move is to castle — drag the king onto its rook.
Chess960 twist: use the unusual starting setup of the pieces.
Difficulty 1340 ShuffleRating — club-player level.
White to move — find the best continuation
How to recognize this tactic
Chess960 castling still ends with king and rook on the classical squares (g1/f1 or c1/d1), but the path can be unusual. Watch which squares the king crosses and whether castling here opens a file, drops a defender or walks into a 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.
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 d1, queen c7, rook a1 g1, bishop d2, knight c3, pawn a2 b2 c2 f2 h2 e4.
Black: king e8, queen d4, rook d8, bishop f5 f8, knight b4 e7, pawn c4 g6 a7 h7.
12 white and 11 black pieces are on the board; the puzzle position arises after move 18.
The position in numbers
White are ahead by 1 points of material (31 against 30; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on d1, the black king on e8.
It is White to move on move 18, with 44 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 4. Files fully open (no pawns of either colour): d — natural highways for the rooks and queen. Half-open for White: g.
Black hold the bishop pair, an edge in open lines. The White king has 4 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
18. O-O-O Nxa2+ 19. Nxa2 Qxe4 20. Nb4
Why it works
- Great move! king to c1 keeps the pressure (+2.4).
- Well found: knight to a2 (+2.8).
- Strong! knight to b4 is the sharp choice (+2.7).
- You reach a winning position (+2.7).
- If instead Nxa2+, then Nxa2 and you stay on top.
Move by move
- 18. O-O-O — king to a1
Types in this puzzle
Castling to safety
One move — castling — whisks the king out of mortal danger.
Castling to safety: the only escape from the attack is to castle — one move whisks the king to g1 or c1 and brings the rook into play as a bonus. In Chess960 this leap can cross half the board, which is exactly why it slips out of sight. Whenever your king is under pressure, ask first: can I still castle? The typical blunder is throwing that right away with a careless king or rook move.
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.
Mate defense
Mate is threatened — parry it and stay on top.
Mate defense: your opponent is one move from mating you — but it is your turn, and that changes everything. Find the defense that kills the mating threat while keeping your advantage: often a check or a counter-threat that leaves no time for the mate. First name the exact square where the mate would land — otherwise you are defending blind. The mistake is playing a "defensive" move that does not actually remove the threat.
About this position
These pieces come from starting position #662.
SP-662 · ThroneGuard — The king starts in the middle of the back rank, on d or e, and neither knight begins in a corner.
The king starts on d1, the rooks on a1 and e1, the queen on h1.
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.
The bishops stand on c1 and f1; their long diagonals reach h6 and a6 once the d- and e-pawns step aside.
One second-rank pawn starts with no defender at all: f2.
The setup belongs to the ThroneGuard family; read right to left it becomes position 198.
The engine's main line opens with d4, putting a pawn straight into the centre.
Morozov Balance Index: 93 of 100 — class A — most balanced. Engine evaluation of the starting position: +11 centipawns for White (depth 49, 400 000 000 nodes).
Explore position #662Provenance
Mined from the project's engine self-play games.
Pack 010 · SP-662
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