Fun Chess Problem

[Ackbach]

I am by no means in the same stratosphere as Jameson and others on this forum when it comes to chess, but I do enjoy the game. Here's a fun little chess problem. White to play and mate in 2.

 

[girdav]

1. c7, then three possibilities: 1. ... Kxa5 2. Rxa7 #; 1. ... b4 2. c8 Q#; 1. ... Kb7 2. c8 Q#.

 

[Opalg]

1. c7, then three possibilities: 1. ... Kxa5 2. Rxa7 #; 1. ... b4 2. c8 Q#; 1. ... Kb7 2. c8 Q#.

But after 1. c7 b4, 2. c8 Q is not mate because of 2. ... Kxa5.

Spoiler

I think that the key to this problem is to ask what black's previous move must have been, and to see which unusual white move this makes possible.

 

[Jameson]

I don't see a forced mate in two moves.

Spoiler

c7 seems like the best move for white and very importantly black should not respond with Kxa5 as Rxa7 is mate. I see a forced mate in 3 though.
1. c7 b4 2.c8+ Kxa5 3. Rxa7 #

 

[Ackbach]

I don't see a forced mate in two moves.

Spoiler

c7 seems like the best move for white and very importantly black should not respond with Kxa5 as Rxa7 is mate. I see a forced mate in 3 though.
1. c7 b4 2.c8+ Kxa5 3. Rxa7 #

There definitely is a forced mate in two. Try all known possible moves.

 

[chisigma]

The 'intuition' of Opalg is the right way to solve the problem... the only possible last move of black has been b7-b5 so that white can reply axb5 'en passant' with the forced successive moves Ka5 and Rxa7#...

Kind regards

$\chi$ $\sigma$

 

[Ackbach]

Congrats to Opalg and chisigma for their (obviously) correct solutions. I thought this was a particularly neat problem, involving the passage of time.

 

[Jameson]

Nice one. I've seen a whole lot of puzzles but never one where realize en passant was an option was necessary. I'll start considering it with future puzzles