Attack on the uncastled king: bishop to b5 (d3·4)
c9-20173naming 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.
Mate in 2: the first move creates an unstoppable threat, the second delivers mate.
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
Difficulty 1090 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.
Mate in two usually opens with a forcing move — a check, a capture or an unstoppable threat — that strips the king of squares or defenders, so the follow-up mate becomes unavoidable. Look for the first move that leaves the opponent only losing replies.
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.
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 d2, rook c1 f1, bishop d3, knight g3 h3, pawn a2 g2 e3 h4 e5 e6.
Black: king e8, rook c8 f8, bishop b7 c7, knight h8, pawn b4 a5 b5 c5 f5 h5 g6 e7.
13 white and 14 black pieces are on the board; the puzzle position arises after move 18.
The position in numbers
White are ahead by 7 points of material (34 against 27; 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 18, with 43 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 8. Files fully open (no pawns of either colour): d — natural highways for the rooks and queen. Half-open for White: b, c, f.
Black hold the bishop pair, an edge in open lines. 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
18. Bxb5+ Bc6 19. Bxc6#
Why it works
- Great move! bishop to b5 keeps the pressure (#1).
- Well found: bishop to c6 (#).
- The line ends in a forced mate in 2.
- If instead Bc6, then Bxc6# and it is mate.
Move by move
- 18. Bxb5+ — bishop to b5 (capture) with check
- Bc6 — bishop to c6
- 19. Bxc6# — bishop to c6 (capture) and it is checkmate
Types in this puzzle
Mate in 2
A forced checkmate in two moves.
Mate in two: your move, any reply, then the mating blow. Start with the most forcing first moves — checks and sacrifices that shrink the opponent's options to almost nothing. Against every single reply you must have a mate ready, so check them all without exception. The common failure is analyzing the pretty defense and forgetting the boring one.
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.
About this position
These pieces come from starting position #784.
SP-784 · 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 c1 and g1, the queen on d1.
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.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
Every pawn on the second rank is defended from the very first move.
The setup belongs to the ThroneScout family; read right to left it becomes position 175.
The engine's main line opens with c4.
Morozov Balance Index: 1 of 100 — class D — largest edge. Engine evaluation of the starting position: +58 centipawns for White (depth 47, 400 000 000 nodes).
In 50 self-play games White scored 58.0% (95% CI 44.2–70.6%).
Explore position #784Provenance
Mined from the project's engine self-play games.
Pack 007 · SP-784
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