Winning blow: rook to b7 (a7·2)
c9-16144naming 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 4: a forced checkmate in four moves — every reply is covered.
Winning tactic: there is a move that gains a decisive advantage — find it.
Difficulty 2120 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.
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.
This position hides a concrete tactic that wins material or mates. Start with the most forcing candidate moves — checks, captures and threats — and calculate each to a clear end before choosing; the winning line is usually the one the opponent cannot meet.
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 c3, queen g1, rook a7, bishop d5, pawn a2 f3 c4 g4 d6.
Black: king g7, rook b7, pawn a4 f4 e5.
9 white and 5 black pieces are on the board; the puzzle position arises after move 42.
The position in numbers
White are ahead by 14 points of material (22 against 8; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on c3, the black king on g7.
It is White to move on move 42, with 33 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): b, h — natural highways for the rooks and queen. Half-open for White: e.
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
42. Rxb7+ Kf8 43. Rf7+ Kg8 44. d7 a3 45. d8=Q#
Why it works
- Best move. rook to b7 is exactly what the engine plays (#3).
- Spot on — rook to f7 (#2).
- A natural move: pawn to d7.
- Best move. pawn to d8 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead Kf8, then Rf7+ and you win the rook.
Move by move
- 42. Rxb7+ — rook to b7 (capture) with check
- Kf8 — king to f8
- 43. Rf7+ — rook to f7 with check
- Kg8 — king to g8
- 44. d7 — pawn to d7
- a3 — pawn to a3
- 45. d8=Q# — pawn to d8 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 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.
Promotion mate
The pawn promotes — and the new piece mates on the spot.
In a promotion mate the pawn takes its final step and the newborn piece mates on the spot. Sometimes the hero is a knight rather than a queen — it checks from the promotion square in a way no queen can. The sign: the enemy king lingers near the promotion square while your pieces already control its escape routes. When counting pawn races, always check whether the promotion itself is mate — that gains you a full tempo in the evaluation.
About this position
These pieces come from starting position #448.
SP-448 · BastionGuard — Both knights begin inside the board while the king stands on c or f; a position and its mirror twin share this family.
The king starts on f1, the rooks on c1 and h1, the queen on g1.
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.
A bishop starts in the corner on a1: it has a single diagonal, which the b-pawn unlocks, running out to h8.
One second-rank pawn starts with no defender at all: d2.
The setup belongs to the BastionGuard family; read right to left it becomes position 703.
The engine's main line opens with c4.
Morozov Balance Index: 75 of 100 — class A — most balanced. Engine evaluation of the starting position: +19 centipawns for White (depth 45, 400 000 000 nodes).
Explore position #448Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-448
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