Mate in 3: pawn to b5 (c4)
c9-26402naming 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 c2, rook f1, knight e5 e6, pawn d2 e2 h2 c4 f4.
Black: king e8, queen b5, rook g8, pawn g4 g6 e7 h7.
9 white and 7 black pieces are on the board; the puzzle position arises after move 21.
The position in numbers
Black are ahead by 2 points of material (16 against 18; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on c2, the black king on e8.
It is White to move on move 21, with 36 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 5 pawns, Black 4. Files fully open (no pawns of either colour): a, b — natural highways for the rooks and queen. Half-open for White: g.
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
21. cxb5 g3 22. Ra1 gxh2 23. Ra8#
Why it works
- Great move! pawn to b5 keeps the pressure (#2).
- rook to a1 develops smoothly.
- Precise: rook to a8 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead g3, then Ra1 and you win the queen.
Move by move
- 21. cxb5 — pawn to b5 (capture)
- g3 — pawn to g3
- 22. Ra1 — rook to a1
- gxh2 — pawn to h2 (capture)
- 23. Ra8# — rook to a8 and it is checkmate
Types in this puzzle
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.
About this position
These pieces come from starting position #255.
SP-255 · BastionScout — Off-centre king plus a rim knight (a/h): 168 positions carry this shape.
The king starts on c1, the rooks on b1 and f1, the queen on d1.
The king already stands on c1, so castling long moves only the rook, from b1 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: a2.
The setup belongs to the BastionScout family; read right to left it becomes position 608.
The engine's main line opens with f4.
Morozov Balance Index: 83 of 100 — class A — most balanced. Engine evaluation of the starting position: +16 centipawns for White (depth 44, 400 000 000 nodes).
Explore position #255Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-255
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