Attack on the uncastled king: queen to a6 (c4·2)
sf-u-0220naming tag (square·N)Opens in the app if installed, otherwise downloads the APK.
The tactical motive
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
Mate in 3: a forced sequence that ends in checkmate.
Chess960 twist: use the unusual starting setup of the pieces.
Difficulty 1950 ShuffleRating — for advanced tacticians.
White to move — find the best continuation
How to recognize this tactic
An uncastled king in the centre is a standing target. Look for ways to open the central files and diagonals against it with checks and threats before it can shelter — every tempo the king spends in the middle is a chance for a combination.
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.
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.
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 b1, queen c4, rook h1 a2, bishop e6, knight g1, pawn g2 h2 f3 e4 a5 c6.
Black: king b8, queen f8, rook a8 h8, bishop e3, knight f6, pawn e5 f5 b6 d6 g6 a7 c7 h7.
12 white and 14 black pieces are on the board; the puzzle position arises after move 16.
The position in numbers
Black are ahead by 2 points of material (31 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 b1, the black king on b8.
It is White to move on move 16, with 41 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 8. No file is fully open, so the heavy pieces have to be pried in. Half-open for White: b, d.
The White king has 3 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
16. Qa6 Qc8 17. Bxc8 f4 18. Qb7#
Why it works
- Great move! queen to a6 keeps the pressure (#2).
- Well found: bishop to c8 (#1).
- Precise: queen to b7 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Qc8, then Bxc8 and you win the queen.
Move by move
- 16. Qa6 — queen to a6
- Qc8 — queen to c8
- 17. Bxc8 — bishop to c8 (capture)
- f4 — pawn to f4
- 18. Qb7# — queen to b7 and it is checkmate
Types in this puzzle
Ladder mate
Two heavy pieces climb line by line, cutting off every retreat.
The ladder mate uses two heavy pieces climbing rung by rung: one cuts the king off along a line, the other checks on the next line, driving him toward the edge. It is the classic two-rook technique — check, the king retreats one rank, the other rook checks, until mate on the last rank. The only danger is the king creeping close enough to attack one of your rooks. If it does, simply slide that rook to the far side of the same line.
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.
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.
Provenance
Mined from the project's engine self-play games.
Verified by Stockfish at depth 20+.
Solution forcedness confirmed (verified).
Pack 014
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