## Sunday, May 18, 2008

### Sunday puzzle

White to play and mate in two moves.

(Langstaff, 1922)

Jonathan B said...

Am I missing something?

Isn't Ke6 and Rd8 a rather simple mate?

Jonathan B said...

Oh - I suppose Black's going to castle.

Jonathan B said...

Cunning.

Anonymous said...

Can we prove from the position itself that an en passant capture is possible ( ie that black has just "played" Pg5 - that's in quotes cos its a study and no one has played anything really ) or do we infer it because that enables a solution. The end justifies the means, you might say.
Jonathan, you shouldn't be blogging in work time. Tsk,tsk!
Martin S.

Morgan Daniels said...

My thought process was exactly the same as jonathan's on this one. Cunning indeed, love it!

ejh said...

Personally I think this one's a bit unfair, but that's why I chose it...

Jonathan B said...

Well the pawn can't have come from g6 (it would have been check) so if it moved last it must have been g7-g5 - and therefore en passant capture is legal.

1. hxg6 ep 0-0
2. h7 mate

or
1. ... other
2. Rd8 mate

if the black pawn didn't move last the rook or king must have - in which case 0-0 is not legal and therefore 1. Ke6 and 2. Rd8 mate.

Retrograte analysis might very well be able to prove that Black can't have moved his king or rook last move but I'm not sure I can see it yet. Either way White gets to mate in two.

ejh said...

Sir: you have it perfectly. No further analysis is required.

It's from the Barnes, Pick of the best chess problems (Elliot Right Way 1976). The solution section states that it's a "partial analysis problem" which I assume (somebody correct me if I'm wrong) means that some reasoning needs to be given : it also says,

"Of course, if White attempts Key 1 Ke6" (i.e. just 1 Ke6 as opposed to the dual solution given by Jonathan above - ejh) "Black Castle's (sic) out of trouble!" I think the angry flower would be angry.

Anonymous said...

cute little puzzle! should have thougth first though!

alexey hurricane