Mate in 3: pawn to b7 (a6·3)
c9-25248naming 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 g1, rook c1, bishop c6, knight b5, pawn b2 f2 h2 e3 g3 a6.
Black: king b8, queen b7, rook a8 d8, bishop h8, pawn f4 g5 a7 h7.
10 white and 9 black pieces are on the board; the puzzle position arises after move 28.
The position in numbers
Black are ahead by 9 points of material (17 against 26; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on g1, the black king on b8.
It is White to move on move 28, with 36 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 4. Files fully open (no pawns of either colour): c, d — natural highways for the rooks and queen.
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
28. axb7 Rd1+ 29. Rxd1 fxe3 30. bxa8=Q#
Why it works
- Great move! pawn to b7 keeps the pressure (#2).
- Spot on — rook to d1 (#1).
- Precise: pawn to a8 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Rd1+, then Rxd1 and you win the queen.
Move by move
- 28. axb7 — pawn to b7 (capture)
- Rd1+ — rook to d1 with check
- 29. Rxd1 — rook to d1 (capture)
- fxe3 — pawn to e3 (capture)
- 30. bxa8=Q# — pawn to a8 (capture) and it is checkmate
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 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.
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 #699.
SP-699 · BastionGuard — King shifted to c or f, knights kept clear of the edges — 168 positions in all.
The king starts on c1, the rooks on a1 and g1, the queen on b1.
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 449.
The engine's main line opens with c3.
Morozov Balance Index: 4 of 100 — class D — largest edge. Engine evaluation of the starting position: +50 centipawns for White (depth 41, 400 000 000 nodes).
Explore position #699Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-699
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