Mate in 3: rook to a7 (b7)
c9-23620naming 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 a5, rook c1 b7, knight f1 d3, pawn e2 h2 g4 b5 a6.
Black: king a8, queen a7, rook e8, knight f4, pawn e6 f6 h7.
11 white and 7 black pieces are on the board; the puzzle position arises after move 28.
The position in numbers
White are ahead by 10 points of material (30 against 20; 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 a8.
It is White to move on move 28, with 49 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 5 pawns, Black 3. Files fully open (no pawns of either colour): c, d — natural highways for the rooks and queen. Half-open for White: f.
The White king has 4 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
28. Rxa7+ Kxa7 29. Qc7+ Ka8 30. Qb7#
Why it works
- Best move. rook to a7 is exactly what the engine plays (#2).
- Spot on — queen to c7 (#1).
- Precise: queen to b7 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Kxa7, then Qc7+ and you win the queen.
Move by move
- 28. Rxa7+ — rook to a7 (capture) with check
- Kxa7 — king to a7 (capture)
- 29. Qc7+ — queen to c7 with check
- Ka8 — king to a8
- 30. Qb7# — queen to b7 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.
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 #684.
SP-684 · ThroneGuard — King on a central file (d/e) with both knights on inner files — the classic-type setup.
The king starts on d1, the rooks on c1 and h1, the queen on a1.
Castling long simply swaps the two pieces: the king on d1 and the rook on c1 trade places.
The bishops stand on b1 and g1; their long diagonals reach h7 and a7 once the c- and f-pawns step aside.
The pawn on e2 is defended by the king alone — the same soft spot f2 is in the classical setup.
The setup belongs to the ThroneGuard family; read right to left it becomes position 476.
The engine's main line opens with c4.
Morozov Balance Index: 21 of 100 — class D — largest edge. Engine evaluation of the starting position: +36 centipawns for White (depth 44, 400 000 000 nodes).
Explore position #684Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-684
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