Chess endgame puzzle: A knight stands by to help the queen
We like chess puzzles to always have a single solution. Puzzle authors do, too. But in the context of a game against an actual opponent, the problems that come up usually have more than one solution.
As I’m doing research for a computer chess program to be written in Scala, my interest in chess puzzles is in part for teaching a computer how to play against an actual opponent.
Still, it helps if a puzzle has only one correct solution, because if it has multiple correct solutions, that might dilute the pedagogical value of the puzzle, and people might even wonder what the point of it is.
Unless… the multiple correct solutions are so alike that the result is essentially the same.
Like maybe today’s puzzle. Black to play, checkmate one move away if you find a correct solution.
FEN: 1k6/q1p2pB1/1p3PB1/5P2/p1P4n/2R1p3/4P3/4R1K1 b - - 0 1
Just prior to arriving at this position, you were trying to capture your opponent’s pesky bishops.
But you weren’t having much luck at it. At this point, you could play Nxg6, but your opponent would probably respond with cxg6, getting your opponent closer to pawn promotion.
However, an opportunity for checkmate has just opened up.
If you make the right move and your opponent understands what’s coming, they might try to head it off, maybe by trying to get close to your knight, or by having their rook on rank 3 capture your pawn on that same rank.
Or maybe they will move their pawn on file c forward, but they will wish that pawn could move two spaces instead of just one.
Or they might just go ahead and resign. If they don’t resign, you can probably go ahead with your plan, and it will be checkmate right then and there.
This puzzle has at least two correct solutions. If you haven’t figured out what either one is, a big hint I’ve dropped consists of the words “they will wish that pawn could move two spaces instead of just one.”
White being able to put a pawn on c6 would really throw a wrench in Black’s plan. Black would still win, it just would take longer. In that scenario, it takes Stockfish Level 8 nine moves to achieve checkmate against White, requiring one promotion of a pawn to a second queen.
Another hint: Qa5 would be a wrong move for Black. Immediately White would know to protect their rooks, and would probably respond with Rec1. The title of this puzzle is also a hint.
Try your hand at the puzzle and the alternative scenario on Lichess. If you find one correct solution, you can probably figure out what the other solution is.