2024/01/26 DPA: "Hey, A Free Rook!"

Black to move. 

Hanging pieces galore!

White's King is exposed but the back rank is adequately protected.

Black does not want to allow White to castle.

Material is even.

Black's King Rook and Bishop will not be participating.

Black might want to play ... Qxf2+ but White's Bishop guards that square.

There are no viable Queen checks.

1. ... Rxd4  2. Qxc6+ Kd8??  3. Ne6#. 

To avoid that, Black can only play 2. ... Kf7 and allow White to draw by perpetual check:  3. Qe6+ Ke8  4. Qc6+, etc.

So the Bishop is verboten.

Another Rook move:  1. ... Re5+.

If 2. Qxe5 Nxe5  3. Bxe5 Qxc5 and Black has won the heavy exchange [Queen for Rook].

2. Kf1 Qe2+  3. Kg1 Qe1+ loses to 4. Rxe1 Rxe1+  5. Qxe1.  So Black will accept the Queen.

2. Be3 Rxe6

2. Bxe5 but now the Bishop no longer guards f2:  2. ... Qxf2+  3. Kd1 Ne3+  4. Kc1 Qc2#

So moving the King or blocking check simply results in Black winning the heavy exchange.

Capturing the Rook with the Queen leads to a similar conclusion.

Capturing the Rook with the Bishop leads to checkmate.  But I'm betting this will be the solution, just to most dramatically show the reward of the Deflection Sacrifice [Black deflected the Bishop away from guarding f2].

Yeah, I was right.

The key was recognizing the vulnerability of the f2 square and then figuring out how to remove the defender with a Deflection Sac.

.

Note that this does not mean the puzzle is "wrong" or that the opponent "blundered".  Neither did White's response to 1. ... Re5+ somehow affect the solver's ability to find 1. ... Re5+.  It might have surprised the solver but he needs to be prepared for *any* opponent response, whether optimal or not.

This is not a position analysis where optimal moves are played on both sides.  This is a puzzle where sub-optimal moves are fine for the opponent [but not the solver].  This is so that the idea being showcased is as obvious as possible:  if an optimal move is played, the lesson might be obscured in the minutiae of the resultant position.

https://www.chess.com/blog/EnPassantFork/no-the-puzzle-is-not-wrong