2024/04/14 DPA: "A King Without A Castle; A Knight's Delayed Capture"

White to move.

White is down 2 pieces.

It's unknown whether either side can castle so I'm going to assume they can.

1. g7 wins the Knight but if 1. ... O-O-O, Black's King is safe and White won't be able to hold on to the new Queen and is still down a piece.

The only move which looks promising [and is very puzzle-like] is 1. exd6 e.p. <en passant>.  But that's impossible because the Bishop on d7 means the previous move cannot have been 0. ... d5.

1. g7 O-O-O  2. Qh8 Ng6  3. Qxd8+ Qxd8 fails because g8 is protected.

Changing the move order for 1 & 2 leads to the same position.

White would like Black to recapture with the King, which allows him to promote safely and with check.  White would then have R + 7P v B + N + 4P <12 v 10> and a passed g pawn.

1. Qf7+ Qxf7  2. gxf7 Kxf7 loses the precious passed pawn without even winning a piece.

1. O-O-O is too slow due to 1. ... Qg5+  2. Kb1 Qxg6.  If 1. Ke2 to allow the Rook to get to h1, 1. ... O-O-O might be good enough.  2. g7 Ng6  3. Qh7 but Black still has double protection on g8.

Black would love to sac the Knight for the pawn.  As long as the Knight is pinned, it can't move.  But as soon as Black castles, it can.

Can the first move be with the Rook?  Where would it go and for what purpose?  I don't see any.

A pawn move [other than 1. g7]?  The only move that causes any sort of conflict is 1. c4 but Black can ignore that and castle.  Or he can capture and then castle. White gets 2. Rc1 and 3. Rxc4+ but does that threaten Black?

The solution must involve the g pawn, either to successfully promote or to be used as a decoy to accomplish something else [ie winning the Black Queen].

The other problem is technical:  if both 1. g7 & 2. Qh8 and 1. Qh8 & 2. g7 lead to the same position, that means it can't be the solution because there cannot be multiple ways to get to the same position.

But if neither of these are correct and e.p. is disallowed, what else is there?

I tested e.p. and the computer refused to make the move:  this means it's an illegal move.  If it was legal but incorrect, I would have seen the "X" error graphic.  So at least I can discard that idea.

Maybe the idea is to allow Black to castle AND sac the Knight for the pawn in order to get White's Rook to the 7th or 8th rank.

The problem with 1. Ke2 Bb5+  2. Kf3 is that the King is exposed on the f file.  After Black castles, ... Rf8+ becomes a threat.

It would be a great "trap the Queen" puzzle if White had a dark-squared Bishop to place on the d8-h4 diagonal.

White can win the Knight but that's all I can see.

Once Black castles [assuming that's legal], I can't see any further gains.

I don't see any Intermezzos either.

.

Let's re-assess:

• e.p. is not possible [prior move was not 0. ... d5]
• no pawn move [except 1. g7] accomplishes anything
• activating the Rook will take 3 moves:  moving the King, Rh1, then Rh7/h8
  • one move can be eliminated by castling but that allows 1. ... Qg5+ and then 2. ... Qxg6
• moving the Rook doesn't help
• the only Queen move that does anything is 1. Qh8, making room for the pawn
  • 1. ... O-O-O  2. g7 Ng6 is good for Black
• 1. g7 O-O-O  2. Qh8 Ng6 ends up the same as above

Plus the fact that there cannot be 2 solutions leads me to believe that neither 1. g7 nor 1. Qh8 are correct [or, if they are, another 2nd move must be correct].

I just enabled "show legal moves" [in the Settings for the puzzle] and castling is allowed for White but it gave me the idea that maybe it's NOT allowed for Black.  That changes everything.

1. g7 Bc6  2. Qh8 [taking the Knight is incorrect because f8 still has 2 defenders] Kd7  3. g8(=Q) [same comment as before] Ng6  4. Qxa8 Nxh8  5. Qxh8

.

The keys were:

• realizing that castling might not be legal [the option to show legal moves is off by default and I never bothered enabling it until now]
• avoiding taking the Knight but promoting instead
• avoiding trying to save both Queens
  • it might help to realize White is gaining a Rook and Knight but only giving up a pawn [rather than a Queen]

What made this puzzle tough [aside from the fact that assuming Black castling was an option made the puzzle impossible] was that there were three consecutive chances for White to blunder [taking the Knight [twice] and trying to preserve both Queens].

.

For those who think "all of that work just to be up the exchange?", consider that White was down 2 pieces:  this is an 8 point swing in material.