Mate in 3: queen to a6 (a3·2)
c9-20223naming 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 1760 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 c2, queen a3, rook d1 f1, bishop a1 h1, knight b5 d5, pawn a2 f2 h2 b4 e5 f5.
Black: king c8, queen f7, rook d8, bishop a8 h8, knight a6 h6, pawn g4 c5 b6 a7 d7 e7 h7.
14 white and 14 black pieces are on the board; the puzzle position arises after move 16.
The position in numbers
White are ahead by 4 points of material (37 against 33; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on c2, the black king on c8.
It is White to move on move 16, with 52 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 7. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: c, d, g.
The White king has 7 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
16. Qxa6+ Bb7 17. Nxe7+ Qxe7 18. Qxb7#
Why it works
- Best move. queen to a6 is exactly what the engine plays (#2).
- Spot on — knight to e7 (#1).
- Precise: queen to b7 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Bb7, then Nxe7+ and you win the knight.
Move by move
- 16. Qxa6+ — queen to a6 (capture) with check
- Bb7 — bishop to b7
- 17. Nxe7+ — knight to e7 (capture) with check
- Qxe7 — queen to e7 (capture)
- 18. Qxb7# — queen to b7 (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 #339.
SP-339 · 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 d1, the rooks on c1 and f1, the queen on e1.
Castling long simply swaps the two pieces: the king on d1 and the rook on c1 trade places.
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 ThroneGuard family; read right to left it becomes position 323.
The engine's main line opens with g4.
Morozov Balance Index: 89 of 100 — class A — most balanced. Engine evaluation of the starting position: +14 centipawns for White (depth 48, 400 000 000 nodes).
Explore position #339Provenance
Mined from the project's engine self-play games.
Pack 013 · SP-339
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