Chess960 tactic on a8 (b7·2)
c9-12618naming 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: a forcing sequence that ends the game — the king has no escape.
Mate in 4: a forced checkmate in four moves — every reply is covered.
Difficulty 2400 ShuffleRating — expert level — few solve it at first try.
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.
This is a forced mating attack. Start from the enemy king: which of its squares are already covered, and which move takes away the rest while keeping the king in check? Forcing moves — checks and captures — are what turn an attack into mate.
A mate in four is a longer forced net: each of your moves is a check or an irresistible threat, and the king is driven step by step to a square where it is finally trapped. Verify that the defender has exactly one reply at every branch.
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 c1, queen h7, rook d4, bishop e1, knight c3, pawn b2 c2 f2 h2 a4 f6 b7.
Black: king f5, rook g6 a8, pawn h3 a5 c5 g5 e6.
12 white and 8 black pieces are on the board; the puzzle position arises after move 23.
The position in numbers
White are ahead by 12 points of material (27 against 15; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on c1, the black king on f5.
It is White to move on move 23, with 49 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 7 pawns, Black 5. Files fully open (no pawns of either colour): d — natural highways for the rooks and queen. Half-open for White: e, g.
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
23. bxa8=Q c4 24. Qe4+ Kxf6 25. Qexg6+ Ke5 26. Qgg7#
Why it works
- Best move. pawn to a8 is exactly what the engine plays (#3).
- Spot on — queen to e4 (#2).
- Precise: queen to g6 is the top choice (#1).
- Best move. queen to g7 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead c4, then Qe4+ and you win the rook.
Move by move
- 23. bxa8=Q — pawn to a8 (capture)
- c4 — pawn to c4
- 24. Qe4+ — queen to e4 with check
- Kxf6 — king to f6 (capture)
- 25. Qexg6+ — queen to g6 (capture) with check
- Ke5 — king to e5
- 26. Qgg7# — queen to g7 and it is checkmate
Types in this puzzle
Mate in 4+
A long forced mating combination.
Mate in four or longer is a marathon of forcing moves where the grip must never loosen. The tools are the same: checks, double threats and sacrifices that deny the opponent a single free tempo. Do not juggle the whole tree at once — walk the main line all the way to mate first, then verify the side branches. If somewhere the defender finds one quiet move that holds, your very first move was wrong.
Skewer
A line attack forces the valuable piece to move, exposing the one behind it.
A skewer is a pin turned inside out: the valuable piece stands in front and something cheaper hides behind it. The big piece must step aside, and you collect the one that was sheltering in its shadow. Scan for the enemy king or queen sharing a file, rank or diagonal with another enemy piece. The deadliest version comes with check — the king moves, the rook behind it dies.
Counter-strike
Don't defend — answer the threat with a bigger one.
The counter-strike: instead of defending against the threat, you answer with a bigger threat of your own. While your opponent grabs a pawn, you deliver mate — the arithmetic favors you. Look for a counter when direct defenses fail: do you have a check, an attack on the queen, a mating threat? The beginner's error is meeting every threat with a reflexive defense without checking the counterattacking resources first.
About this position
These pieces come from starting position #474.
SP-474 · 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 a1 and g1, the queen on h1.
Castling ends where it always does: king to g1 and rook to f1 on the short side, king to c1 and rook to d1 on the long one.
The bishops stand on e1 and f1; their long diagonals reach a5 and a6 once the d- and e-pawns step aside.
One second-rank pawn starts with no defender at all: b2.
The setup belongs to the ThroneGuard family; read right to left it becomes position 677.
The engine's main line opens with Nc3, bringing the knight out to c3.
Morozov Balance Index: 65 of 100 — class B — balanced. Engine evaluation of the starting position: +22 centipawns for White (depth 48, 400 000 000 nodes).
Explore position #474Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-474
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