Winning blow: rook to b7 (b8·3)
c9-26523naming 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.
A fork made possible by the Chess960 piece placement.
Winning tactic: there is a move that gains a decisive advantage — find it.
Difficulty 1390 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.
A set-up fork needs one preparing move before the fork lands — a check that drives the king onto the forking square, or a capture that lines the targets up. Find the preparation first, then the fork it makes possible.
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 a2, rook b8, bishop c5 g8, pawn b2 c2 d4 h5.
Black: king b5, rook f1, bishop c7, knight b6, pawn d5 a6 c6 h6.
8 white and 8 black pieces are on the board; the puzzle position arises after move 41.
The position in numbers
Material is level — 15 points of pieces on each side (pawn = 1, knight and bishop = 3, rook = 5, queen = 9).
The white king stands on a2, the black king on b5.
It is White to move on move 41, with 23 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 4 pawns, Black 4. Files fully open (no pawns of either colour): e, f, g — natural highways for the rooks and queen. Half-open for White: a.
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
41. Rb7 Bd8 42. Bh7 Rf3 43. Bd3+ Rxd3 44. cxd3
Why it works
- Great move! rook to b7 keeps the pressure (+5.2).
- bishop to h7 develops smoothly.
- Precise: bishop to d3 is the top choice (+5.4).
- Best move. pawn to d3 is exactly what the engine plays (+5.4).
- You win decisive material (+5.4).
- If instead Bd8, then Bh7 and you stay on top.
Move by move
- 41. Rb7 — rook to b7
- Bd8 — bishop to d8
- 42. Bh7 — bishop to h7
- Rf3 — rook to f3
- 43. Bd3+ — bishop to d3 with check
- Rxd3 — rook to d3 (capture)
- 44. cxd3 — pawn to d3 (capture)
Types in this puzzle
Setup fork
The random setup allows a fork that classical chess never sees.
A setup fork is a double attack that exists only because of the unusual starting squares — in classical chess these targets never stand side by side. Look for pairs of undefended pieces on your opponent's back rank and for squares from which a knight or pawn hits both at once. Such forks usually appear within the first moves, before the pieces disperse. In every new position, note right away which starting pieces are defended by no one.
Quiet move
No check, no capture — yet this modest move decides the game.
A quiet move gives no check and takes nothing — yet it decides the game by creating an unstoppable threat or stealing the king's last square. This is the hardest class of moves: the eye hunts for loud blows while a modest shift does the winning. The clue: every forcing try runs into a defense, so seek the move that strengthens the threat or takes squares away. Train yourself to ask: what if I neither capture nor check, but quietly improve?
Endgame tactic
Tactics live in the endgame too — strike while material is scarce.
Tactics do not retire when the queens come off: forks, pins and double attacks live on in the endgame. With so little material left, every tactical loss is almost always decisive. The signs are the usual ones — undefended pieces, king and piece on one line, a pawn about to promote. Even in a "technical" ending, scan for a shot before every move, both yours and your opponent's.
About this position
These pieces come from starting position #669.
SP-669 · BastionGuard — King shifted to c or f, knights kept clear of the edges — 168 positions in all.
The king starts on c1, the rooks on a1 and e1, the queen on h1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
The bishops stand on d1 and g1; their long diagonals reach h5 and a7 once the e- and f-pawns step aside.
The pawn on b2 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 200.
The engine's main line opens with e4, putting a pawn straight into the centre.
Morozov Balance Index: 5 of 100 — class D — largest edge. Engine evaluation of the starting position: +49 centipawns for White (depth 45, 400 000 000 nodes).
Explore position #669Provenance
Mined from the project's engine self-play games.
Pack 010 · SP-669
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