Mate in 3: queen to a5 (a4·2)
c9-25460naming 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 e1, queen a4, rook a1 f1, bishop c4 f4, knight b1 e2, pawn a2 b2 f2 h2 c3 g3.
Black: king d8, rook a8 f8, bishop h3 h8, knight g4, pawn a7 b7 e7 f7 g7 h7.
14 white and 12 black pieces are on the board; the puzzle position arises after move 13.
The position in numbers
White are ahead by 12 points of material (37 against 25; 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 13, with 41 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): d — natural highways for the rooks and queen. Half-open for White: e.
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
13. Qa5+ Kd7 14. Qc7+ Ke8 15. Bb5#
Why it works
- Great move! queen to a5 keeps the pressure (#2).
- Spot on — queen to c7 (#1).
- Precise: bishop to b5 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Kd7, then Qc7+ and you stay on top.
Move by move
- 13. Qa5+ — queen to a5 with check
- Kd7 — king to d7
- 14. Qc7+ — queen to c7 with check
- Ke8 — king to e8
- 15. Bb5# — bishop to b5 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.
Relative pin
A piece shields a more valuable one behind it — moving it loses material.
In a relative pin the piece shields not its king but something valuable behind it, usually the queen. Moving is legal but costly, because the piece behind falls. Look for three units on one line: your long-range piece, a cheaper enemy piece, and an expensive one hiding behind. Beware the classic trap — a relatively pinned piece can still move with check or a bigger threat, so verify before you cash in.
About this position
These pieces come from starting position #615.
SP-615 · ThroneGuard — Both knights start on inner files (b–g) while the king sits centrally on d or e — one of 204 positions filed here.
The king starts on e1, the rooks on a1 and f1, the queen on d1.
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.
One second-rank pawn starts with no defender at all: h2.
The setup belongs to the ThroneGuard family; read right to left it becomes position 242.
The engine's main line opens with c4.
Morozov Balance Index: 94 of 100 — class A — most balanced. Engine evaluation of the starting position: +10 centipawns for White (depth 50, 400 000 000 nodes).
Explore position #615Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-615
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