Chess

[cinelli]

I think it is high time we had another chess puzzle.

.  --- --- --- --- --- --- --- ---
8 |   |   |   |   |   |   |   |   |
   --- --- --- --- --- --- --- ---
7 |   | p |   | p |   | p |   |   |
   --- --- --- --- --- --- --- ---
6 | P | B |   | k |   | P |   |   |
   --- --- --- --- --- --- --- ---
5 |   |   |   |   | p | P |   |   |
   --- --- --- --- --- --- --- ---
4 | P | N |   | p | P |   |   |   |
   --- --- --- --- --- --- --- ---
3 |   | P | p | P |   |   |   |   |
   --- --- --- --- --- --- --- ---
2 |   |   | K |   |   |   |   |   |
   --- --- --- --- --- --- --- ---
1 | R |   | N | B |   |   |   |   |
   --- --- --- --- --- --- --- ---
    a   b   c   d   e   f   g   h

White, shown here as red, is to mate in five moves. Every white move is accurate and every black move forced.

Cinelli

[cinelli]

Hint: look for the white piece most distant from the battlefield.

Cinelli

[BBLSP1]

I have been trying with this one - focusing on the King's limited movement. Made more difficult by me not having a board to hand to more clearly see what is going on! Now coming into a busy few days at work, but thanks for the hint.

Really posting just to let you know that your post has not gone unnoticed - at least by me.

[jfgw]

I have been trying with this one - focusing on the King's limited movement. Made more difficult by me not having a board to hand to more clearly see what is going on! Now coming into a busy few days at work, but thanks for the hint.

Really posting just to let you know that your post has not gone unnoticed - at least by me.

I am not getting far either.

You can experiment here, https://lichess.org/editor/8/1p1p1p2/PB ... 4_w_KQkq_- Since black's moves are all forced, you can get the machine to play black.

The above link is for white to play. This can be changed easily to "Black to play".

Click "continue from here", PLAY WITH THE MACHINE, and click the white king to play white. It will record your moves and you can step back and try something different. Note that you cannot step back from a finished game so avoid a stalemate or you will have to start again.

The above link assumes that the next player cannot capture en passant. This, however, does not appear to be part of a possible solution.

Julian F. G. W.

[CryptoPlankton]

With thanks to jfgw for providing that link to play with it, spoiler:


1. Bh5 bxa6
2. Bxf7 a5
3. Na6 Kc6
4. Bd5+ Kd6
5. Bc7#

[UncleEbenezer]

With thanks to jfgw for providing that link to play with it, spoiler:

Um, how is Black's fourth move there forced?

I didn't get Julian's link to work: as soon as I click on the pop-up play board it disappears leaving me back at the editor. But then, I'm happy to retain my excuse for not attempting chess problems.

[CryptoPlankton]

With thanks to jfgw for providing that link to play with it, spoiler:

Um, how is Black's fourth move there forced?

I didn't get Julian's link to work: as soon as I click on the pop-up play board it disappears leaving me back at the editor. But then, I'm happy to retain my excuse for not attempting chess problems.

Ouch! Probably best not to look at these things at 3.30am when suffering from insomnia - thought it seemed a bit too easy.

Didn't work for me on my laptop, but on Android phone the link takes me directly to a position where I can play both sides (that's how I was able to be stupid enough to miss Black's other move).

Back to the drawing (chess) board...

[jfgw]

I didn't get Julian's link to work: as soon as I click on the pop-up play board it disappears leaving me back at the editor. But then, I'm happy to retain my excuse for not attempting chess problems.

Are you clicking one of the kings? (Not the ones on the board!) Click the white one to play white, click the black one to play black or click the bigger white/black one in the middle if you want the machine to decide. If you click on the board itself, it takes you back to the board editor.

It works for me on Firefox 66.0.5 (64 bit) and Opera 74.0.3729.169 (Official Build) (64-bit). If I try it in IE11, I get an "OUTDATED BROWSER" message saying, "You must get a better browser to continue using Lichess" with links to Firefox and Opera.

Julian F. G. W.

[BBLSP1]

Lichess works fine for me on Chrome - Thanks for this jfgw.

As to the puzzle - I just can't see any solution where every black move is forced, treating this as being only one legal move available to black each turn (rather than the move which delays mate the longest).

[UncleEbenezer]

Ouch! Probably best not to look at these things at 3.30am when suffering from insomnia - thought it seemed a bit too easy.
.

Minor perk of the 'net: insomniacs are not alone. I too should've been asleep when I posted.

Are you clicking one of the kings? (Not the ones on the board!) Click the white one to play white, click the black one to play black or click the bigger white/black one in the middle if you want the machine to decide.

Um, I got that board as a pop-up, with a board too small to read easily. Whatever you're talking about may have been hidden behind it or off the screen. I tried clicking the white king on the board, which was the only one I could see. But then, it was the wee hours and I was only trying it 'cos I couldn't sleep (and was following up to CryptoPlankton).

Trying it again now (from a different 'puter with a much bigger screen), it works as you describe.

[jfgw]

As to the puzzle - I just can't see any solution where every black move is forced, treating this as being only one legal move available to black each turn (rather than the move which delays mate the longest).

That was my interpretation but I found this,

Just one small note.There are moves that are forced because they are the only legal moves and moves that are "practically forced" because they are the only ones that don't lose the game.

https://www.chess.com/forum/view/game-a ... orced-move

And this,

forced move
A move that is the only one that does not result in a serious disadvantage for the moving player. Forced can also be used to describe a sequence of moves for which the player has no viable alternative, for example "the forced win of a piece" or "a forced checkmate". In these cases the player cannot avoid the loss of a piece or checkmate, respectively.[161]

https://en.wikipedia.org/wiki/Glossary_of_chess#F

Among others.

A forced move could, threfore, be one where any alternative move would allow white to win on his next turn, for example.

Julian F. G. W.

[UncleEbenezer]

A forced move could, threfore, be one where any alternative move would allow white to win on his next turn, for example.

Julian F. G. W.

I don't think that argument really works from a "resign" position. Which black is obviously in, at least as soon as white does something to remove the stalemate option.

[CryptoPlankton]

Okay, at the risk of making a fool of myself again, spoiler:

1. Bf3 bxa6
2. Ne2 a5
3. Re1 axb4
4. Nxd4 exd4
5. e5#

[cinelli]

Many congratulations to CryptoPlankton for the correct solution. I was just about to post another hint, but I didn't want to give the game away because I think this is the best chess problem, by Fritz Giegold, I have ever seen.

Thanks also to Julian for the lichess.org link.

Cinelli