Mate in 3: queen to a5 (d2·2)
c9-25468naming 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.
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.
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 b2, queen d2, knight c5 d5, pawn c2 b3 e3 d4 f4.
Black: king a8, queen e7, rook g2, knight d6 f8, pawn b5 f5 c6 f6 d7 h7.
9 white and 11 black pieces are on the board; the puzzle position arises after move 25.
The position in numbers
Black are ahead by 6 points of material (20 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 b2, the black king on a8.
It is White to move on move 25, with 33 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 5 pawns, Black 6. Files fully open (no pawns of either colour): a, g — natural highways for the rooks and queen. Half-open for White: h.
The White king has 6 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
25. Qa5+ Kb8 26. Qc7+ Ka8 27. Nb6#
Why it works
- Great move! queen to a5 keeps the pressure (#2).
- Spot on — queen to c7 (#1).
- Precise: knight to b6 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Kb8, then Qc7+ and you stay on top.
Move by move
- 25. Qa5+ — queen to a5 with check
- Kb8 — king to b8
- 26. Qc7+ — queen to c7 with check
- Ka8 — king to a8
- 27. Nb6# — knight to b6 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.
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.
Corner mate
Driven into the corner, the king runs out of squares.
The corner mate catches a king driven into the corner, where it has only three neighboring squares — all of them taken away or blocked. The corner is the worst home for a king, because the attacker needs to control the fewest squares there. Herd the king toward the corner with checks and never let it slip back toward the center. Cut off the escape routes before the final check, and the mate practically assembles itself.
About this position
These pieces come from starting position #818.
SP-818 · BastionScout — The king starts one file off-centre, on c or f, and a knight begins in a corner.
The king starts on c1, the rooks on b1 and g1, the queen on e1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
The second rank carries 2 pawns with no defender at all: a2, h2.
The setup belongs to the BastionScout family; read right to left it becomes position 135.
The engine's main line opens with d4, putting a pawn straight into the centre.
Morozov Balance Index: 86 of 100 — class A — most balanced. Engine evaluation of the starting position: +15 centipawns for White (depth 45, 400 000 000 nodes).
Explore position #818Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-818
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