Chess960 tactic on b2 (c4)
c9-15135naming 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: a forcing sequence that ends the game — the king has no escape.
Mate in 4: a forced checkmate in four moves — every reply is covered.
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.
This is a forced mating attack. Start from the enemy king: which of its squares are already covered, and which move takes away the rest while keeping the king in check? Forcing moves — checks and captures — are what turn an attack into mate.
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.
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 d1, rook b3 e8, bishop h1, knight c4 d8, pawn a2 c2 d2 g2 h2 b5.
Black: king a4, rook b8 h8, bishop e4, knight g8, pawn c5 b6 a7 d7 e7 h7.
12 white and 11 black pieces are on the board; the puzzle position arises after move 18.
The position in numbers
White are ahead by 3 points of material (25 against 22; pawn = 1, knight and bishop = 3, rook = 5, queen = 9) — the tactic has to convert or outweigh that.
The white king stands on d1, the black king on a4.
It is White to move on move 18, with 35 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 6 pawns, Black 6. Files fully open (no pawns of either colour): f — 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
18. Nb2+ Ka5 19. Ra3+ Kxb5 20. c4+ Kb4 21. Ra4#
Why it works
- Great move! knight to b2 keeps the pressure (#3).
- Spot on — rook to a3 (#2).
- Precise: pawn to c4 is the top choice (#1).
- Best move. rook to a4 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead Ka5, then Ra3+ and you stay on top.
Move by move
- 18. Nb2+ — knight to b2 with check
- Ka5 — king to a5
- 19. Ra3+ — rook to a3 with check
- Kxb5 — king to b5 (capture)
- 20. c4+ — pawn to c4 with check
- Kb4 — king to b4
- 21. Ra4# — rook to a4 and it is checkmate
Types in this puzzle
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.
About this position
These pieces come from starting position #643.
SP-643 · ThroneGuard — A central king (d or e) and two knights tucked onto inner files: the family that holds the standard array, SP-518.
The king starts on d1, the rooks on b1 and e1, the queen on f1.
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: h2.
The setup belongs to the ThroneGuard family; read right to left it becomes position 211.
The engine's main line opens with g4.
Morozov Balance Index: 89 of 100 — class A — most balanced. Engine evaluation of the starting position: +14 centipawns for White (depth 43, 400 000 000 nodes).
Explore position #643Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-643
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