Mate in 3: queen to a5 (a4)
c9-18044naming 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 d1, queen a4, rook e1 b3, bishop c2, pawn d2 h2 a3 f4 g5 d6.
Black: king d8, queen c8, rook f7 b8, pawn d3 c5 h5 g6 d7.
11 white and 9 black pieces are on the board; the puzzle position arises after move 29.
The position in numbers
White are ahead by 4 points of material (28 against 24; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on d1, the black king on d8.
It is White to move on move 29, with 36 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 5. Files fully open (no pawns of either colour): b, e — natural highways for the rooks and queen. Half-open for White: c.
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
29. Qa5+ Rb6 30. Qxb6+ Qc7 31. Qxc7#
Why it works
- Best move. queen to a5 is exactly what the engine plays (#2).
- Spot on — queen to b6 (#1).
- Precise: queen to c7 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Rb6, then Qxb6+ and you win the rook.
Move by move
- 29. Qa5+ — queen to a5 with check
- Rb6 — rook to b6
- 30. Qxb6+ — queen to b6 (capture) with check
- Qc7 — queen to c7
- 31. Qxc7# — queen to c7 (capture) and it is checkmate
Types in this puzzle
Supported queen mate
The queen delivers mate face to face, protected by a friend.
The supported queen mate is the most common pattern of all: the queen lands next to the king and mates because a friendly piece or pawn protects her. The king is helpless — capturing is impossible, and the queen covers every neighboring square herself. Hunt for a protected square beside the enemy king: a knight, bishop or pawn eyeing it turns her invasion into mate. Verify one thing — that the square really is defended, or the king eats her.
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.
Win the pinned piece
The pinned piece cannot run — attack it again and win it.
A pinned piece cannot flee, which means you can win it outright by attacking it one more time. Count attackers against defenders: if you outnumber them, the piece is yours. The best extra attacker is a pawn, since it costs less than anything it might capture. Do not rush the capture — build up the pressure first, then harvest.
About this position
These pieces come from starting position #620.
SP-620 · ThroneScout — The king starts on d or e while at least one knight begins in a corner.
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.
The bishops stand on b1 and g1; their long diagonals reach h7 and a7 once the c- and f-pawns step aside.
The second rank carries 2 pawns with no defender at all: b2, g2.
The setup belongs to the ThroneScout family; read right to left it becomes position 252.
The engine's main line opens with f4.
Morozov Balance Index: 1 of 100 — class D — largest edge. Engine evaluation of the starting position: +63 centipawns for White (depth 43, 400 000 000 nodes).
In 50 self-play games White scored 62.0% (95% CI 48.2–74.1%).
Explore position #620Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-620
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