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        riddles >> medium >> Pawn Walls (Chess)
        
(Message started by: THUDandBLUNDER on Jul 4^th, 2005, 12:34am)

Title: Pawn Walls (Chess)
Post by THUDandBLUNDER on Jul 4^th, 2005, 12:34am

PART 1:

White to play and win.

Title: Re: Pawn Walls (Chess)
Post by TenaliRaman on Jul 4^th, 2005, 5:01am

Hope, i am right atleast with this post :(
[hide]
1. b5,c6xb5(or a6xb5)
2. a5(or c5),b6xa5(or b6xc5)
We have freed one of the pawns at this stage, which can go ahead and convert.
[/hide]

-- AI

Title: Re: Pawn Walls (Chess)
Post by THUDandBLUNDER on Jul 4^th, 2005, 9:38am

Yes, that's the idea.

However, on closer inspection I see I should have placed the pawn walls on the 5th and 7th ranks (not 4th and 6th).
With the pawns as they are, both sides will queen for a draw.

PART 2: White to play and win.
(This time the position is correct.)

Title: Re: Pawn Walls (Chess)
Post by FiBsTeR on May 12^th, 2008, 7:14am

Here's what I got:

[hide]

CASE 1:

1. e5 dxe5
2. b5 ...

and the game plays like PART 1.

CASE 2:

1. e5 fxe5
2. fxe5

At this point, black cannot play the d-pawn, or else the game becomes PART 1 again.

Black also cannot play the a-pawn, or else white plays 3. bxa5 bxa5 4. exd6 Ke8 5. c5 and white can win by marching his king up, since black has no smart pawn moves and his king is tied to white's pawn.

Black also cannot play the c-pawn, or else white plays 3. b5 axb5 (cxd4 for black would have white queen and check first) 4. a5 bxa5 5. cxb5 cxd4 and white queens and checks first, leading to a white win.

Black also cannot play the b-pawn, or else white plays axb5 with the d-pawn preventing black's c5.

Black also cannot play either of the g- or h-pawns, or else white plays 3. exd5. Here, black can only move the king or play b5, where the former loses to b5 and the latter loses to axb5 (note the d-pawn stops black from using PART 1).

So that leaves black to play the king with Ke8, and thus the game finishes with:

3. exd6 Kd7
4. c5 bxc5

When white plays dxc5, black has no choice but to sit and wait for white's king to come up and help his a- and b-pawns to promotion.

[/hide]

Title: Re: Pawn Walls (Chess)
Post by ThudanBlunder on May 12^th, 2008, 8:44am

on 05/12/08 at 07:14:33, FiBsTeR wrote:

Here's what I got:

CASE 1:

1. e5 dxe5
2. b5 ...

and the game plays like PART 1.

But the difference here is that after
2........cxb5
3. a5 bxa5
4. c5
the black king on f8 can easily catch the White c-pawn.
So that doesn't work.

Title: Re: Pawn Walls (Chess)
Post by Hippo on May 12^th, 2008, 1:30pm

I have spent alot of time with it (of course without a chessboard ;)).
I guess Ke* is the correct start.
Main variant ... b5 cxb5 a5 bxa5 c5 ... Black king have to guard the c pawn and ... g5 fxg5 h5 gxh5 f5 ...

Ke2 is required for white to be able to catch a pawn fast enough (race in response to c5).

... I didn't check it exactly ... just a guess ;)

Title: Re: Pawn Walls (Chess)
Post by ThudanBlunder on May 12^th, 2008, 1:45pm

on 05/12/08 at 13:30:06, Hippo wrote:

Ke2 is required for white to be able to catch a pawn fast enough (race in response to c5).

Nope, the White king is not needed to win.

Title: Re: Pawn Walls (Chess)
Post by Barukh on May 18^th, 2008, 11:04pm

Here’s my take on this.

[hideb]
1. b5 cb 2. a5 ba 3. c5 dc 4. dc Ke8 5. c6 Kd8

At this point, Black king can not move too far from the “c” file. White can now start the same maneuver at the King’s side (by moving g5) and get a promoting pawn at file “f”. It is then impossible for the Black king to simultaneously catch “c” and “f” pawns.
[/hideb]

That’s just a single line of play but I think it’s the strongest defense for Black.

Title: Re: Pawn Walls (Chess)
Post by ThudanBlunder on May 19^th, 2008, 5:02am

on 05/18/08 at 23:04:02, Barukh wrote:

Here’s my take on this.
That’s just a single line of play but I think it’s the strongest defence for Black.

Barukh, in your variation Black can improve on the defensive 5.....Kd8 by making the stronger counter-threat 5.....a4, and Black is threatening to queen in three moves with check.

Title: Re: Pawn Walls (Chess)
Post by Hippo on May 19^th, 2008, 1:03pm

Yes, ... this was why I was guessing the Ke2 at first ...

Title: Re: Pawn Walls (Chess)
Post by ThudanBlunder on May 19^th, 2008, 5:08pm

on 05/19/08 at 13:03:06, Hippo wrote:

Yes, ... this was why I was guessing the Ke2 at first ...

Barukh has the right idea but the wrong first move.

Title: Re: Pawn Walls (Chess)
Post by Hippo on May 20^th, 2008, 2:10am

In that case [hide]you must start with g5 to fix the black king first and follow by b5 to queen any pawn.[/hide]

Title: Re: Pawn Walls (Chess)
Post by ThudanBlunder on May 20^th, 2008, 9:06am

on 05/20/08 at 02:10:33, Hippo wrote:

In that case [hide]you must start with g5 to fix the black king first and follow by b5 to queen any pawn.[/hide]

Neither 1.b5 nor 1.g5 will effect a decisive breakthrough. The wall needs to be weakened first.

Title: Re: Pawn Walls (Chess)
Post by Hippo on May 20^th, 2008, 2:43pm

So what remains ;) ... either d5 or e5. I have tried d5 and it seems it works. ... main variant:
1. d5 exd5 2. exd5 c5 3. a5 bxa5 4. b5 axb5 5. cxb5 Ke7 6. b6 Kd7 7. b7 kc7 8. g5 fxg5 9. h5 gxh5 10. f5 ...

Title: Re: Pawn Walls (Chess)
Post by ThudanBlunder on May 20^th, 2008, 3:55pm

on 05/20/08 at 14:43:20, Hippo wrote:

1. d5 exd5 2. exd5 c5 3. a5 bxa5 4. b5 axb5 5. cxb5 Ke7 6. b6 Kd7 7. b7 kc7 8. g5 fxg5 9. h5 gxh5 10. f5 ...

That looks right, Hippo.

What if 1...cxd5?

Title: Re: Pawn Walls (Chess)
Post by Hippo on May 22^nd, 2008, 7:53am

on 05/20/08 at 15:55:17, ThudanBlunder wrote:

That looks right, Hippo.

What if 1...cxd5?

I hope it shortenes the main variant by one move only ... 2. a5 bxa5 3. b5 axb5 4. cxb5 Ke7 5. b6 Kd7 6. b7 Kc7 7. g5 fxg5 8. h5 gxh5 9. f5 ...

Title: Re: Pawn Walls (Chess)
Post by ThudanBlunder on May 22^nd, 2008, 2:44pm

on 05/22/08 at 07:53:49, Hippo wrote:

I hope it shortenes the main variant by one move only ... 2. a5 bxa5 3. b5 axb5 4. cxb5 Ke7 5. b6 Kd7 6. b7 Kc7 7. g5 fxg5 8. h5 gxh5 9. f5 ...

Many a slip 'twixt cup and lip, 9.....exf5 :P

So White has to play exd5 at some stage earlier to get rid of that pawn.

When you have more time you can check this (http://www.gothicchess.com/javascript_8x8_chess_endings.html) out. :)

Title: Re: Pawn Walls (Chess)
Post by Hippo on May 23^rd, 2008, 12:56am

on 05/22/08 at 14:44:08, ThudanBlunder wrote:

Many a slip 'twixt cup and lip, 9.....exf5 :P

So White has to play exd5 at some stage earlier to get rid of that pawn.

Ok it would be equally long 10. exf5 ...