I see that this works, but still don't understand why. Please explain! - Chess Forums

JPSterling

Aug 28, 2023

0

#1

[white to move]

1.a7 is met with 1...Bd4+, and ultimately white is never able to promote neither the h- nor a-pawn [1.a7 Bd4+ 2.Kf3 Bxa7 3.Nc2 Bb8 4.h7 Be5] Yet, if before pushing the a-pawn, I sacrifice my Knight with 1.Nxb5 then play 2.a7, I'm later able to promote the h-pawn [1.Nxb5 cxb5 2.a7 Bd4+ 3.Kf3 Bxa7 4. Ke4 Ke6 5.h7 f5+ 6.Kd3 f4 7.h8=Q].

My brain is simply not comprehending how playing 1.a7 fails, yet 1.Nxb5...2.a7 works. It seems like the Knight move is independent of the promotion, as it does not create any sort of a blockade after the trades. I can see that the biggest difference is that 1.Nxb5 later allows for 4.Ke4 which prevents the Bishop from returning to attack the promotion square on the h-file, but why is Ke4 possible in the second line but not the first? Is there a tempo being gained somewhere, if so, where? What am I not understanding? Someone please explain.

justbefair

Aug 28, 2023

0

#2

JPSterling wrote:

[white to move]

1.a7 is met with 1...Bd4+, and ultimately white is never able to promote neither the h- nor a-pawn [1.a7 Bd4+ 2.Kf3 Bxa7 3.Nc2 Bb8 4.h7 Be5] Yet, if before pushing the a-pawn, I sacrifice my Knight with 1.Nxb5 then play 2.a7, I'm later able to promote the h-pawn [1.Nxb5 cxb5 2.a7 Bd4+ 3.Kf3 Bxa7 4. Ke4 Ke6 5.h7 f5+ 6.Kd3 f4 7.h8=Q].

My brain is simply not comprehending how playing 1.a7 fails, yet 1.Nxb5...2.a7 works. It seems like the Knight move is independent of the promotion, as it does not create any sort of a blockade after the trades. I can see that the biggest difference is that 1.Nxb5 later allows for 4.Ke4 which prevents the Bishop from returning to attack the promotion square on the h-file, but why is Ke4 possible in the second line but not the first? Is there a tempo being gained somewhere, if so, where? What am I not understanding? Someone please explain.

I still can't explain it either but I thought that this diagram might help.

AtaChess68

Aug 28, 2023

0

#3

Ke4 to prevent …Bd4 is met by …f5+.

In the first line the d5 square is not free for the white king (the square is protected by the black c6 pawn).

In the second line the black c6 pawn is gone and white can get out of check to Kd5, still preventing …Bd4.

JPSterling

Aug 28, 2023

0

#4

justbefair wrote:

JPSterling wrote:

[white to move]

1.a7 is met with 1...Bd4+, and ultimately white is never able to promote neither the h- nor a-pawn [1.a7 Bd4+ 2.Kf3 Bxa7 3.Nc2 Bb8 4.h7 Be5] Yet, if before pushing the a-pawn, I sacrifice my Knight with 1.Nxb5 then play 2.a7, I'm later able to promote the h-pawn [1.Nxb5 cxb5 2.a7 Bd4+ 3.Kf3 Bxa7 4. Ke4 Ke6 5.h7 f5+ 6.Kd3 f4 7.h8=Q].

My brain is simply not comprehending how playing 1.a7 fails, yet 1.Nxb5...2.a7 works. It seems like the Knight move is independent of the promotion, as it does not create any sort of a blockade after the trades. I can see that the biggest difference is that 1.Nxb5 later allows for 4.Ke4 which prevents the Bishop from returning to attack the promotion square on the h-file, but why is Ke4 possible in the second line but not the first? Is there a tempo being gained somewhere, if so, where? What am I not understanding? Someone please explain.

I still can't explain it either but I thought that this diagram might help.

Thank you for the diagram. I went over it, over and over, as I had previously, and I am seeing that the c-pawn seems to be the primary factor. Sacrificing the Knight gets it to shift to the b-file. I THINK that's the primary factor, anyway. There's just no way my brain would be able to figure this puzzle out by mental calculation.

JPSterling

Aug 28, 2023

0

#5

AtaChess68 wrote:

Ke4 to prevent …Bd4 is met by …f5+.
In the first line the d5 square is not free for the white king (the square is protected by the black c6 pawn).
In the second line the black c6 pawn is gone and white can get out of check to Kd5, still preventing …Bd4.

That does make sense, and it took me watching through each line somewhere around 20x to finally spot it. It just seems to be a scenario that my brain is simply not wired well enough for Chess to be able to foresee the difference when trying to calculate.

AtaChess68

Aug 28, 2023

0

#6

Same here. Not a chance that I would have found Nxb5 on my own.

Cobra2721

Aug 28, 2023

0

#7

Truly a chess move

JPSterling

Aug 28, 2023

0

#8

AtaChess68 wrote:

Same here. Not a chance that I would have found Nxb5 on my own.

Thank you for saying that. I feel better. Usually I understand where I went wrong and why the better move is better, but I was beating myself up for struggling so much with this one, even after knowing the answer.

JPSterling

Aug 28, 2023

0

#9

cogadhtintreach wrote:

Truly a chess move

Indeed, and it tells me how much differently real Chess players brains function compared to my own.

ChessDude009

Aug 28, 2023

0

#10

JPSterling wrote:

cogadhtintreach wrote:

Truly a chess move

Indeed, and it tells me how much differently real Chess players brains function compared to my own.

If it helps you, Nxb5 wins for a reason that we don't understand at a first glance. You'd think it would be made to deflect a piece, but instead it is made so that the c pawn will not be able to stop the king from travelling to d5 later on.

Laskersnephew

Aug 28, 2023

0

#11

Apologies to anyone who has already made this point

The knight sacrifice displaces the pawn from c6 to b5. This gives the white king access to the d5 square so that he can prevent the bishop from taking the a7 pawn and then returning to capture the h6 pawn.

JPSterling

Aug 28, 2023

0

#12

ChessDude009 wrote:

JPSterling wrote:

cogadhtintreach wrote:

Truly a chess move

Indeed, and it tells me how much differently real Chess players brains function compared to my own.

If it helps you, Nxb5 wins for a reason that we don't understand at a first glance. You'd think it would be made to deflect a piece, but instead it is made so that the c pawn will not be able to stop the king from travelling to d5 later on.

I do see that now, thanks to everyone's input it has finally clicked. I have a question for you...you have very high rating...how easy/difficult would it be for you to spot this move in a game?

JPSterling

Aug 28, 2023

0

#13

Laskersnephew wrote:

Apologies to anyone who has already made this point

The knight sacrifice displaces the pawn from c6 to b5. This gives the white king access to the d5 square so that he can prevent the bishop from taking the a7 pawn and then returning to capture the h6 pawn.

Thank you for your input, it's greatly appreciated. This position was really making my head pound.

skeldol

Aug 29, 2023

0

#14

I imagine that's at least a master level move, requires a lot of calculation to see why the sac is required (black skewers the king and Queen from c1) and then you have to spot the sac.

Arisktotle

Aug 29, 2023

0

#15

Yes, 1.Nxb5!! is a master level move. @Laskersnephew gave the critical variation where white attempts to switch the move order: 1.a7? Bd4+! 2.Kf3 Bxa7 3.Nxb5 Bb8!! and black holds. It's the question and exclamation marks that tell the story as much as the moves!

Laskersnephew

Aug 29, 2023

0

#16

It’s a master move if you figure it out at the board. But is you look at a a bunch of endgame problems, the idea of using your king deny the bishop a critical square will become familiar. There’s a good reason that they recommend doing endgame studies. I could never figure that out cold

Ialwayswin20233

Aug 29, 2023

0

#17

comment on my blog to get pinned

Cobra2721

Aug 30, 2023

0

#18

Life is roblox

mpaetz

Aug 30, 2023

0

#19

It's often helpful to "reverse engineer" endgame positions: start with envisioning the position you need to get to win, then see if there is a way to get there. In this case it's getting the a pawn to a7 while the black king can't stop it (to divert the bishop) and getting your own king to d5 to prevent the bishop from returning to a position covering h8. The knight sacrifice is easier to find when you see that you need to divert black's c pawn.