# Chess problem: White to mate in 2

• Galileo
In summary: Pawn's Mate?In summary, this is a great retrograde problem that is not easily solved. White must move a pawn en passent to create a position where checkmate is inevitable.

#### Galileo

Homework Helper
I'd like to share with you guys one of the most beautiful chess problems I've ever seen.

See the attachment for the setup.

It's white's turn. Mate in two.

#### Attachments

• chess.gif
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Nice one!

edit: scrap it! :grumpy:

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1. c7 Kb7(...Kxa5 2. Rxa7++; ...b5 2. Qc8++) 2. Qc8++

Drat,i can't see the attachement.:grumpy: I thought the bugger would keep happening to someone else.

Daniel.

quark said:
1. c7 Kb7(...Kxa5 2. Rxa7++; ...b5 2. Qc8++) 2. Qc8++

Nope. Black responds with b5-b4 (the pawn is already on b5) and white can then only check in 2 ways, neither giving mate.

Any luck with the attachment Dex?

Yes, quite amusing, answer in white: Pawn takes pawn en passent

dextercioby said:
Drat,i can't see the attachement.:grumpy:
Me either. It says I don't have permission to access that page. :(

I first got that message too. Click "Log Out" and you will be able to see it. Go figure.

First I will post and then read the other solution.

Not quite sure but if the previous step is a5 b5 then enpassant and white wins in second step. Or in continuation to my earlier game Qc8+ Kxa5 and Rxa7++.

Now I will see what Jimmy says.

This problem is an excellent example of what the logician and chess fan Raymond Smullyan calls "retrograde analysis".

The clue to solve the problem is:
What MUST black's last move have been?

However, quark's solution seems valid.

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There may be another way; but this should work.

Pawn at C6 to C7.
- If Black takes Pawn at A5 with King,
- Rook at A8 to A7. Check Mate!

- If Black moves Pawn at B5 to B4,
- Pawn now at C7 to C8 (change to Queen). Check Mate!

- If Black moves King from A6 to B7,
- Pawn now at C7 to C8 (change to Queen). Check Mate!

Those are the only three moves black can do after moving from C6 to C7.

Check Mate!

As for what Black had to have done last move :

He moved his Pawn from B6 to B5.

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No, Rahmus, that is an IMPOSSIBLE history of the game!
Think again..

quark said:
First I will post and then read the other solution.

Not quite sure but if the previous step is a5 b5 then enpassant and white wins in second step. Or in continuation to my earlier game Qc8+ Kxa5 and Rxa7

Now I will see what Jimmy says.

I thought enpassant could only be used as that Pawns first move? I guess I don't know chess as well as I thought I did.

Rahmuss said:
I thought enpassant could only be used as that Pawns first move?
Quite so..

arildno said:
No, Rahmus, that is an IMPOSSIBLE history of the game!
Think again..

Did I mess up in my denoting of where the pieces are? Or why is it impossible? I don't see it. I do see one lapse... hmmm... let's think this through again... Wait!... I guess one of those would be a check mate in three moves... darn...

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The white king is now at c5.
Thus, if black's last move was to move his pawn from b6 to b5 (creating the situation displayed), that would have meant that white was IN CHECK from that pawn and chose not to move his king on his previous move, or alternatively positioned his king at c5 as his last move. But, either way, this is illegal for white to do..

Hence, b6-b5 cannot have been Black's last move.

arildno said:
Quite so..

Ahhh... I see. I had the rules of enpassant a little wrong. So blacks move in the turn before was:

Pawn at B7 to B5.

Right?

And with that in mind my answer has changed. Although I did have a good strategy; but not knowing Blacks last move was the trick. So:

Enpassant from white Pawn at A5 to B6. Then Black is forced to move his King from A6 to A5, and then white moves his Rook from A8 to A7.

Check Mate!

Is that correct?

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arildno said:
However, quark's solution seems valid.
Yes, but the continuation will require 3 moves in total.

Galileo said:
Yes, but the continuation will require 3 moves in total.
Yes, I just discovered that.
Do you have Smullyan's books on this?

I learned a possible two move check mate from start; but white has to be really dumb and black has to know what's going on. Even still... it would be fun to see it actually happen. Short game.

White moves his Pawn from F2 to F3
Black moves his Pawn from E7 to E6

White moves his Pawn from G2 to G4
Black moves his Queen from D8 to H4

Check Mate!

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Rahmuss said:
I learned a possible two move check mate from start; but white has to be really dumb and black has to know what's going on. Even still... it would be fun to see it actually happen. Short game.
It's appropriately enough called Fool's mate.

Actually, I've lost a game in less moves than that in a tournament once:
I had a dreadful hang-over and did not want to play chess at 9.00 A.M
So, here's my shortest tournament game:

White: Me
Black: E.D

1. e2-e4 (offers a draw) c7-c6 (declines by making a move)
I resigned, and went back to sleep..

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Galileo said:
Yes, but the continuation will require 3 moves in total.
Nonetheless, standard chess jargon calls this a mate in 2. Go figure.

arildno said:
Yes, I just discovered that.
Do you have Smullyan's books on this?

Thanks.

No, I found this somewhere else in a book on heuristics.
I do have a Smullyan's book "The Riddle of Scheherazade", but I don't think this puzzle is in there.

Galileo said:
Thanks.

No, I found this somewhere else in a book on heuristics.
I do have a Smullyan's book "The Riddle of Scheherazade", but I don't think this puzzle is in there.
He has published at least two books solely concerned with retrograde analysis:
A "Sherlock Holmes" book, which includes, among other things, a big treasure hunt by Holmes&Watson and solving a murder mystery.

"Arabian Knights", which I've managed to lose..

Anyways, you can find their titles on this page somewhere (books 6&14):
http://www.alibris.com/search/books/author/Smullyan,%20Raymond

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It is a mate in 2 and kind of cute

1. a5xb5 en-passant k-a5 (...b5-b4 2. Rxc7++) 2.Rxc7++

1.c6-c7 will yeald a mate in 3 but no mate in 2

And to clear up the rule for en-passant...

On its first move if a pawn moves forward 2 spaces. Any pawn that it passed may capture it as if it had only moved one space.

So in this problem blacks previous move had to be b7-b5.We know this becouse blace has no other legal moves that allow for this position. This allows White to capture the b5 pawn on the b6 square. As if it had only moved 1 space.

Hope this cleared it up =-)

xJuggleboy said:
So in this problem blacks previous move had to be b7-b5.We know this becouse blace has no other legal moves that allow for this position.
Hope this cleared it up =-)

Black player seems to be very dumb. I would rather play ...b6+ 2. a5xb6 Kb7 etc.

Not that I will get advantage but I annoy the white player a bit as I will loose anyway.

quark said:
I would rather play ...b6+ 2. a5xb6 Kb7 etc.
It would still have been a mate in two. Kb7 is not a legal move, Ka5 is forced and checkmate follows. Remember, capturing en passent after ...b5 is pretty much the same thing as a normal capture after ...b6.

In a chess problem it is pointless to question the wisdom of black's moves. It is a given that black is a loser. We can, however, question the legality of the position. The situation on the board should be the result of moves that no matter how unwise, are legal.

By the way, I believe it the custom in chess problems not to have pieces on the board that do not participate in the mate (with the possible exception of the white king which must be on the board in any case). If that is so, then since one of white's pawns is extraneous, it should be removed.

oopsie, I was dumber

jimmysnyder said:
By the way, I believe it the custom in chess problems not to have pieces on the board that do not participate in the mate (with the possible exception of the white king which must be on the board in any case). If that is so, then since one of white's pawns is extraneous, it should be removed.

Thats not always the case... There are a few I have seen that there are a few extra pieces that are there... also its possible it came from a game. In which case all pieces that were in the game are on the board.

It depends on the chess problem, jimmysnyder.
You are correct that irrelevant pieces should not be included in the so-called "studies", which for that reason is considered the "purest" form of chess problem.

We need more chess problems

I agree... Too bad I can't find any.

Only one possible solution - I assume this has been already solved:
pxp ep kxa5
rxa7 mate

Chronos said:
Only one possible solution - I assume this has been already solved:
pxp ep kxa5
rxa7 mate