Chess960 tactic on b7 (c6·3)
c9-08957naming tag (square·N)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
Position on the board
White: king a2, queen e5, rook c1 e1 f8, bishop e2, pawn f2 e3 b5 c6 d7.
Black: king a7, queen b7, rook b8, pawn f3 a5 b6 h6 c7.
11 white and 8 black pieces are on the board; the puzzle position arises after move 36.
Solution & explanation
Main line
36. cxb7 Rxf8 37. Qxc7 Rb8 38. d8=Q Rxb7 39. Qdb8#
Why it works
- Best move. pawn to b7 is exactly what the engine plays (#3).
- Spot on — queen to c7 (#2).
- A natural move: pawn to d8.
- Best move. queen to b8 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead Rxf8, then Qxc7 and you win the queen.
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 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.
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 #874.
SP-874 · BastionScout — A knight on the a- or h-file, king on c or f — the mirror twin lands here as well.
The king starts on c1, the rooks on b1 and d1, the queen on a1.
The king already stands on c1, so castling long moves only the rook, from b1 to d1.
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: h2.
The setup belongs to the BastionScout family; read right to left it becomes position 85.
The engine's main line opens with b4.
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 #874Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-874
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