2024/01/27 DPA: "Hanging Pieces Thesis"
Black to move.
White has back rank weakness but he can block any check with Bf1.
Also, if given the time, he can play h3 or g3 to give the King luft ["air"; space to move].
Any Knight move opens up the Queen to play ... Qa1+.
We also need to deflect/decoy/attract the Bishop away from the d3-f1 diagonal so he cannot block check with Bf1.
Is there a Knight move that accomplishes this?
1. ... Nd3 looks promising because it threatens the Queen so cannot be ignored.
This move is also nice because it prevents 2. Qc1 to protect the back rank.
The obvious response is to capture the Knight: 2. Bxd3 Qa1+ 3. Bf1 and Black has nothing. IF the King and Bishop were one square further towards the corner AND Black's Rook was on a8, Black could play 3. ... Qxg1+ 4. Kxg1 Ra1+ 5. Qc1 Rxc1#.
But those 2 conditions don't exist. The latter is possible but not the former.
What if Black recaptures? 2. ... exd3, which also opens up the e file for the Rook.
The problem is that this is not a forcing move, which means White has a chance to play g3/h3 and the back rank mate threat vanishes.
1. ... Nf3+ works on the same principle but allows White 2. gxf3, which opens up g2 for escape. So Black probably does not want this.
Elapsed total time: 13 m
Note that all 3 White pieces are undefended.
1. ... Qc7 threatens the Rook but also X-Rays the White Queen through the Black Knight.
2. Rc6, defending the Rook and attacking the Queen, loses to 2. ... Nf3+ 3. Qxf3 [3. gxf3 loses to 3. ... Qxf4] exf3 4. Rxc7 fxe2, the star move: White cannot stop the pawn from promoting.
Elapsed total time: 30m
Can White play a better 2nd move? He could sac the Rook with 2. Rxg6+ but that just loses a Rook for a pawn, an admission that 1. ... Qc7 was the correct answer.
2. Re6 still loses to 2. ... Nf3+ 3. Qxf3 exf3 4. Rxe8+ Kf7 and now both Rook and Bishop are en prise. If White saves the Rook, he loses the Bishop AND Black will promote. So White will give up the Rook and Black has a Q v B endgame. Completely winning.
If White doesn't move his Rook, Black takes it. White has no checks.
I don't see anything White can do to avoid huge loss of material; it's only a matter of which losing line he chooses.
2. Rc6 is the most puzzle-like opponent response because it gives Black 2 chances to lose his nerve so I predict that will be it.
Elapsed total time: 35m
That was it.
The big picture key was recognizing White's hanging pieces and that no back rank checkmate existed, as tempting as it looked. I frequently overlook this as I'm geared towards seeking a checkmate.
The small picture key was envisioning what the board looked like after 4. ... fxe2: without that foresight, Black would have concluded it was just an even exchange and looked elsewhere [which is what I did initially before taking a closer look].
.
Since it will inevitably come up, no, the puzzle was not "wrong" and the opponent did not "blunder".
Yes, White played sub-optimally with 2. Rc6: as my analysis above outlined [confirmed by Stockfish], White had other moves that were marginally less bad. The significant choice was 4. Rxc7, taking the Queen, when 4. gxf3 or 4. Bf1 would have stayed in the game but with a -5 edge for Black.
This gigantic advantage means 4. Rxc7 was not a blunder [alters the course of the match; ie turns a win into a draw or loss] but rather just a sub-optimal move [avoids checkmate but results in a completely losing position].
Remember that a puzzle is not a position analysis, which does provide optimal moves for both sides. A puzzle is a lesson designed to showcase an idea, tactic, or motif and the puzzle creator gets to decide how to best accomplish this. Sometimes, it's done with sub-optimal moves. This in no way detracts from the puzzle nor should it stop the solver from coming up with the best solver's moves; what the opponent does is beyond the solver's control.
Note that how easily the solver could convert this to a win is irrelevant: the solution is the optimal play for Black, regardless of what the opponent does.
https://www.chess.com/blog/EnPassantFork/no-the-puzzle-is-not-wrong