Mate in 3: rook to c8 (b8)
c9-22000naming 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 3: a forced sequence that ends in checkmate.
A fork made possible by the Chess960 piece placement.
Difficulty 1990 ShuffleRating — for advanced tacticians.
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.
In a mate in three every move must be forcing; the defender should never get a free tempo. Find the check or threat that herds the king, calculate the single defence to each, and confirm the net closes on the third move.
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.
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 e1, queen a7, rook f1 b8, bishop c6, knight d1, pawn c2 d2 e2 h2 g3 f4.
Black: king d8, rook f7, bishop c8 h8, knight c7 g8, pawn e3 c5 d6 e7 g7 h7.
12 white and 12 black pieces are on the board; the puzzle position arises after move 16.
The position in numbers
White are ahead by 8 points of material (31 against 23; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on e1, the black king on d8.
It is White to move on move 16, with 49 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 6. Files fully open (no pawns of either colour): a, b — natural highways for the rooks and queen.
Black 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
16. Rxc8+ Kxc8 17. Qb7+ Kd8 18. Qb8#
Why it works
- Best move. rook to c8 is exactly what the engine plays (#2).
- Spot on — queen to b7 (#1).
- Precise: queen to b8 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Kxc8, then Qb7+ and you stay on top.
Move by move
- 16. Rxc8+ — rook to c8 (capture) with check
- Kxc8 — king to c8 (capture)
- 17. Qb7+ — queen to b7 with check
- Kd8 — king to d8
- 18. Qb8# — queen to b8 and it is checkmate
Types in this puzzle
Mate in 3
A forced checkmate in three moves.
Mate in three is a forced staircase: each of your moves narrows the opponent's choices, and the third one ends the game. Look for the start among checks and sacrifices — quiet first moves are rare in mating problems, but deliciously sneaky. Keep the tree in your head: every defense gets its own branch. Do not stop calculating after move two — see the final mating picture with your own eyes.
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.
Royal fork
A fork with check: the king must move, and the second piece is lost.
A royal fork is a fork with check — one of the two targets is the king itself. The check must be answered first, so nobody is left to rescue the second piece. Look for squares where your piece gives check and simultaneously attacks an undefended queen or rook. It is the most reliable fork of all, because your opponent literally has no choice.
About this position
These pieces come from starting position #583.
SP-583 · ThroneGuard — A central king (d or e) and two knights tucked onto inner files: the family that holds the standard array, SP-518.
The king starts on e1, the rooks on b1 and f1, the queen on a1.
The kingside rook already stands on f1, so castling short moves only the king, from e1 to g1.
A bishop starts in the corner on h1: it has a single diagonal, which the g-pawn unlocks, running out to a8.
The second rank carries 2 pawns with no defender at all: c2, h2.
The setup belongs to the ThroneGuard family; read right to left it becomes position 274.
The engine's main line opens with b4.
Morozov Balance Index: 37 of 100 — class C — noticeable edge. Engine evaluation of the starting position: +30 centipawns for White (depth 43, 400 000 000 nodes).
Explore position #583Provenance
Mined from the project's engine self-play games.
Pack 014 · SP-583
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