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Normal Topic Skewer vs. X-ray, Difference? (Read 9015 times)
Smyslov_Fan
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Re: Skewer vs. X-ray, Difference?
Reply #6 - 06/11/13 at 02:18:41
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ReneDescartes wrote on 06/10/13 at 20:30:53:




It's not academic: the x-ray attack is not just a variant of a skewer. It is fundamentally different in that in an x-ray two pieces attack one enemy piece or square, whereas in a skewer one piece attacks two enemy pieces or squares. Furthermore , as a focused attack rather than a double attack, it is, unlike a skewer, unable to win material on its own in the absence of a further element such as a restricting net or trapped piece,  function motif, fork (as in the example above) or pin. CT-Art, Reinfeld, Chess Informant, etc. regard the x-ray as a separate (if not too common) motif useful for learning and include a separate section for it in their practical exercise sets.


Chess Informant's Encylcopedia of Chess Middlegames: Combinations (1980) has a category for "X-Ray Attack (Rentgen), but not for "skewer". 

When teaching the tactic, I like to use the term X-Ray because the tactic treats the key piece as if it's almost invisible and focuses on what is behind that piece!

Here are a couple examples from ECM:






  
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Re: Skewer vs. X-ray, Difference?
Reply #5 - 06/10/13 at 22:38:23
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I agree most of us don't actually "learn in terms of these categories". We learn by seeing lots of positions and move-sequences with similar patterns, and internalizing those patterns.

But if you're writing a book sorted by theme, you need some chapter headlines! LeMoir's are perfectly good, and we don't need to memorize them anyway.
  

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ReneDescartes
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Re: Skewer vs. X-ray, Difference?
Reply #4 - 06/10/13 at 20:30:53
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GeneM wrote on 06/09/13 at 04:33:22:
Your illustration of the distinction looks good.

This level of academic parsing reminds me of David LeMoir's book-
"How to Become a Deadly Chess Tactician".
His book has section names for tactical motifs that include:

Simple Silent Sacrifice
Secondary Line Clearance
Substitution
Complex Silent Sacrifice
Brilliant Blunders
The Unpinning Sacrifice
The Shunning Sacrifice
Ambush!
Tail-Lights
The Quiet Follow-Up
The Sting in the Tail
Quiet Stings

No matter how accurate all these excessively academic categories might be, I doubt many chess enthusiasts could really learn in terms of these categories.
. .


It's not academic: the x-ray attack is not just a variant of a skewer. It is fundamentally different in that in an x-ray two pieces attack one enemy piece or square, whereas in a skewer one piece attacks two enemy pieces or squares. Furthermore , as a focused attack rather than a double attack, it is, unlike a skewer, unable to win material on its own in the absence of a further element such as a restricting net or trapped piece,  function motif, fork (as in the example above) or pin. CT-Art, Reinfeld, Chess Informant, etc. regard the x-ray as a separate (if not too common) motif useful for learning and include a separate section for it in their practical exercise sets.

« Last Edit: 06/10/13 at 22:40:31 by ReneDescartes »  
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Re: Skewer vs. X-ray, Difference?
Reply #3 - 06/09/13 at 23:49:27
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I don't recall hearing the expression "X-ray" at all when I was younger (i.e. when dinosaurs roamed the earth) but I became aware of it some years ago in contexts such as, say, White has a rook on e1 and Black's queen is on e7, but there is some piece clutter between the two; the white rook could be said to be exerting "X-ray pressure" on the black queen, which is a tactical weakness where it stands, an accident waiting to happen, just as a loose piece often is.

Hope this helps.
  
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Re: Skewer vs. X-ray, Difference?
Reply #2 - 06/09/13 at 04:33:22
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Your illustration of the distinction looks good.

This level of academic parsing reminds me of David LeMoir's book-
"How to Become a Deadly Chess Tactician".
His book has section names for tactical motifs that include:

Simple Silent Sacrifice
Secondary Line Clearance
Substitution
Complex Silent Sacrifice
Brilliant Blunders
The Unpinning Sacrifice
The Shunning Sacrifice
Ambush!
Tail-Lights
The Quiet Follow-Up
The Sting in the Tail
Quiet Stings

No matter how accurate all these excessively academic categories might be, I doubt many chess enthusiasts could really learn in terms of these categories.
. .
  

GeneM , CastleLong.com , FRC-chess960
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Re: Skewer vs. X-ray, Difference?
Reply #1 - 06/06/13 at 18:25:33
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Judging from the examples, it seems that Silman considers the following to be an X-ray:

White piece A and a Black piece B are opposing each other along a rank (or file, or diagonal). White then moves piece C to a square behind B on the same rank. Even though C is not directly guarded by any White piece, it is indirectly guarded by A.

I don't know if this is correct, and I don't think I have ever learned a name for this theme (not even in my native language). But it seems to be Silman's interpretation of an X-ray.

This is quite different from a skewer, where White piece A threatens Black piece B along a rank (or file, or diagonal), and when B moves, A can capture piece C further behind on the same rank.

So, if I have understood Silman correctly, this is an X-ray:

* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
*
1.Bf6+

while this is a skewer:

* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
* * * * * * * *
*
1.Bb2+
  
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Skewer vs. X-ray, Difference?
06/06/13 at 00:59:17
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/***
Jeremy Silman wrote (emphasis mine), on 2013/05/23, at

http://www.chess.com/article/view/x-ray---chess-taser

***/
"The first tactical themes one should master are pins, skewers, forks, ... I’ve covered these (and more) in some detail in the last few months, ...
This week we’ll be taking a look at the interesting, very effective, but oddly little-known tactical device known as the X-ray ..."


++++++++++++++


** What is the difference between Skewer vs. X-ray? **


I thought they were synonyms. Apparently so does the author of this Wikipedia.org article:


http://en.wikipedia.org/wiki/Skewer_(chess)

"In chess, a skewer (or X-ray attack) is an attack upon two pieces in a line and is similar to a pin. In fact, a skewer is sometimes described as a "reverse pin"; the difference is that in a skewer, the more valuable piece is in front of the piece of lesser or equal value."

. .
  

GeneM , CastleLong.com , FRC-chess960
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