Chess960 tactic on a7 (a8)
c9-28513naming 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 2400 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 g1, queen a8, rook c1 f1, bishop a1 h1, knight b4, pawn h2 d3 g3 d4.
Black: king c7, queen d2, rook c5 g6, knight e6, pawn f4 f5 b6 a7 d7 e7 h7.
11 white and 12 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 (32 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 g1, the black king on c7.
It is White to move on move 18, with 44 legal replies to weigh — only the line that keeps the advantage solves the puzzle.
White keeps 4 pawns, Black 7. Files fully open (no pawns of either colour): c — natural highways for the rooks and queen. Half-open for White: a, b, e, f.
White hold the bishop pair, an edge in open lines. The White king has 0 empty squares to step to right now — the fewer they are, the closer a mating net.
Solution & explanation
Main line
18. Qxa7+ Kc8 19. Qb7+ Kd8 20. Qb8+ Rc8 21. Rxc8#
Why it works
- Best move. queen to a7 is exactly what the engine plays (#3).
- Spot on — queen to b7 (#2).
- Precise: queen to b8 is the top choice (#1).
- Best move. rook to c8 is exactly what the engine plays (#).
- The line ends in a forced mate in 4.
- If instead Kc8, then Qb7+ and you stay on top.
Move by move
- 18. Qxa7+ — queen to a7 (capture) with check
- Kc8 — king to c8
- 19. Qb7+ — queen to b7 with check
- Kd8 — king to d8
- 20. Qb8+ — queen to b8 with check
- Rc8 — rook to c8
- 21. Rxc8# — rook to c8 (capture) 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.
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.
Counter-strike
Don't defend — answer the threat with a bigger one.
The counter-strike: instead of defending against the threat, you answer with a bigger threat of your own. While your opponent grabs a pawn, you deliver mate — the arithmetic favors you. Look for a counter when direct defenses fail: do you have a check, an attack on the queen, a mating threat? The beginner's error is meeting every threat with a reflexive defense without checking the counterattacking resources first.
About this position
These pieces come from starting position #275.
SP-275 · ThroneGuard — King home on d or e, knights kept off the a- and h-files — the family of the standard starting array.
The king starts on d1, the rooks on c1 and f1, the queen on g1.
Castling long simply swaps the two pieces: the king on d1 and the rook on c1 trade places.
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: a2.
The setup belongs to the ThroneGuard family; read right to left it becomes position 579.
The engine's main line opens with g4.
Morozov Balance Index: 75 of 100 — class A — most balanced. Engine evaluation of the starting position: +19 centipawns for White (depth 50, 400 000 000 nodes).
Explore position #275Provenance
Mined from the project's engine self-play games.
Pack 015 · SP-275
Similar puzzles
In your browser or in the Android app. Nothing to install · Free, no ads