Mate in 2: rook to a6 (a4)
c9-26793naming 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 2: the first move creates an unstoppable threat, the second delivers mate.
A fork made possible by the Chess960 piece placement.
Difficulty 1320 ShuffleRating — club-player level.
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.
Mate in two usually opens with a forcing move — a check, a capture or an unstoppable threat — that strips the king of squares or defenders, so the follow-up mate becomes unavoidable. Look for the first move that leaves the opponent only losing replies.
A set-up fork needs one preparing move before the fork lands — a check that drives the king onto the forking square, or a capture that lines the targets up. Find the preparation first, then the fork it makes possible.
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 b2, rook d1 a4, bishop h1 g3, knight e3 c5, pawn c3 d4.
Black: king a7, queen h6, rook d8, bishop d7 h8, knight g6, pawn h3 g4 b5 a6 c7 h7.
9 white and 12 black pieces are on the board; the puzzle position arises after move 29.
The position in numbers
Black are ahead by 5 points of material (24 against 29; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on b2, the black king on a7.
It is White to move on move 29, with 53 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 2 pawns, Black 6. Files fully open (no pawns of either colour): e, f — natural highways for the rooks and queen. Half-open for White: a, b, g, h.
The White king has 7 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
29. Rxa6+ Kb8 30. Ra8#
Why it works
- Great move! rook to a6 keeps the pressure (#1).
- Spot on — rook to a8 (#).
- The line ends in a forced mate in 2.
- If instead Kb8, then Ra8# and it is mate.
Move by move
- 29. Rxa6+ — rook to a6 (capture) with check
- Kb8 — king to b8
- 30. Ra8# — rook to a8 and it is checkmate
Types in this puzzle
Mate in 2
A forced checkmate in two moves.
Mate in two: your move, any reply, then the mating blow. Start with the most forcing first moves — checks and sacrifices that shrink the opponent's options to almost nothing. Against every single reply you must have a mate ready, so check them all without exception. The common failure is analyzing the pretty defense and forgetting the boring one.
Setup fork
The random setup allows a fork that classical chess never sees.
A setup fork is a double attack that exists only because of the unusual starting squares — in classical chess these targets never stand side by side. Look for pairs of undefended pieces on your opponent's back rank and for squares from which a knight or pawn hits both at once. Such forks usually appear within the first moves, before the pieces disperse. In every new position, note right away which starting pieces are defended by no one.
Win the pinned piece
The pinned piece cannot run — attack it again and win it.
A pinned piece cannot flee, which means you can win it outright by attacking it one more time. Count attackers against defenders: if you outnumber them, the piece is yours. The best extra attacker is a pawn, since it costs less than anything it might capture. Do not rush the capture — build up the pressure first, then harvest.
About this position
These pieces come from starting position #667.
SP-667 · BastionGuard — The king starts one file off-centre, on c or f, with neither knight in a corner.
The king starts on c1, the rooks on a1 and d1, the queen on g1.
The king already stands on c1, so castling long moves only the rook, from a1 to d1.
A bishop starts in the corner on h1: it has a single diagonal, which the g-pawn unlocks, running out to a8.
One second-rank pawn starts with no defender at all: e2.
The setup belongs to the BastionGuard family; read right to left it becomes position 193.
The engine's main line opens with f4.
Morozov Balance Index: 13 of 100 — class D — largest edge. Engine evaluation of the starting position: +41 centipawns for White (depth 45, 400 000 000 nodes).
Explore position #667Provenance
Mined from the project's engine self-play games.
Pack 010 · SP-667
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