Attack on the uncastled king: knight to b7 (a5·29)
c9-28048naming 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.
Uncastled king: the enemy king is stuck in the centre — punish it before it castles.
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.
An uncastled king in the centre is a standing target. Look for ways to open the central files and diagonals against it with checks and threats before it can shelter — every tempo the king spends in the middle is a chance for a combination.
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 f1, rook g1 b8, knight a5 d5, pawn d3 g3 a4 e4 g4.
Black: king d8, rook a2 h8, knight c8, pawn f6 d7 g7 h7.
10 white and 8 black pieces are on the board; the puzzle position arises after move 28.
The position in numbers
White are ahead by 4 points of material (21 against 17; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on f1, the black king on d8.
It is White to move on move 28, with 27 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): b, c — natural highways for the rooks and queen. Half-open for White: f, h.
The White king has 1 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
28. Nb7+ Ke8 29. Nd6+ Kd8 30. Rxc8#
Why it works
- Great move! knight to b7 keeps the pressure (#2).
- Well found: knight to d6 (#1).
- Precise: rook to c8 is the top choice (#).
- The line ends in a forced mate in 3.
- If instead Ke8, then Nd6+ and you stay on top.
Move by move
- 28. Nb7+ — knight to b7 with check
- Ke8 — king to e8
- 29. Nd6+ — knight to d6 with check
- Kd8 — king to d8
- 30. Rxc8# — rook to c8 (capture) 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.
Royal fork
A fork with check: the king must move, and the second piece is lost.
A royal fork is a fork with check — one of the two targets is the king itself. The check must be answered first, so nobody is left to rescue the second piece. Look for squares where your piece gives check and simultaneously attacks an undefended queen or rook. It is the most reliable fork of all, because your opponent literally has no choice.
Uncastled king
The king lingered in the middle — punish the delay.
Punishing the uncastled king: your opponent delayed castling, and now his king is stuck on its starting square under fire. In Chess960 this is deadlier than in classical chess — the king may start in the center or near the edge, and the familiar defensive setups simply do not apply. The signs: the victim still holds castling rights, and the files toward his king are half-open. Open lines before the king manages to hide.
About this position
These pieces come from starting position #690.
SP-690 · ThroneGuard — King on a central file (d/e) with both knights on inner files — the classic-type setup.
The king starts on d1, the rooks on b1 and h1, the queen on c1.
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.
The second rank carries 2 pawns with no defender at all: a2, f2.
The setup belongs to the ThroneGuard family; read right to left it becomes position 455.
The engine's main line opens with b4.
Morozov Balance Index: 94 of 100 — class A — most balanced. Engine evaluation of the starting position: +10 centipawns for White (depth 43, 400 000 000 nodes).
Explore position #690Provenance
Mined from the project's engine self-play games.
Pack 012 · SP-690
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