Mate in 3: queen to b3 (h3)
c9-25929naming 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 1630 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 h3, rook c1 f1, bishop b1 g1, knight c5, pawn b2 d2 e2 g2 h2 f5.
Black: king b5, rook f7 d8, bishop b8, knight e5 a8, pawn a3 d4 a6 f6 e7 g7 h7.
13 white and 13 black pieces are on the board; the puzzle position arises after move 18.
The position in numbers
White are ahead by 8 points of material (34 against 26; 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 b5.
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 7. Files fully open (no pawns of either colour): c — 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
18. Qb3+ Kc6 19. Qb7+ Kd6 20. Ne4#
Why it works
- Best move. queen to b3 is exactly what the engine plays (#2).
- Spot on — queen to b7 (#1).
- Precise: knight to e4 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Kc6, then Qb7+ and you stay on top.
Move by move
- 18. Qb3+ — queen to b3 with check
- Kc6 — king to c6
- 19. Qb7+ — queen to b7 with check
- Kd6 — king to d6
- 20. Ne4# — knight to e4 and it is checkmate
Types in this puzzle
Knight mate
The knight lands the killing blow from its unique angle.
In a knight mate the final blow comes from the knight — the only piece whose check can never be blocked. That makes it lethal against a cramped king: only a king move or capturing the knight itself can help. The sign: the squares around the king are occupied or covered, and there is a hop from which the knight checks while staying untouchable. Bring the knight over early — it is slower than the long-range pieces, but its strike cannot be parried.
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.
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.
About this position
These pieces come from starting position #316.
SP-316 · 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 d1 and f1, the queen on c1.
The kingside rook already stands on f1, so castling short moves only the king, from e1 to g1.
The bishops stand on b1 and g1; their long diagonals reach h7 and a7 once the c- and f-pawns step aside.
One second-rank pawn starts with no defender at all: g2.
The setup belongs to the ThroneScout family; read right to left it becomes position 364.
The engine's main line opens with f4.
Morozov Balance Index: 2 of 100 — class D — largest edge. Engine evaluation of the starting position: +56 centipawns for White (depth 44, 400 000 000 nodes).
Explore position #316Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-316
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