I have a question about a move that most players don't play, at least the ones I play against.
Below are 2 diagrams, in the first: Does white need to defend at a?
If not why? Normally everyone i played against play elsewhere (includeing myself) and balck never cuts.
I ask this because there is a joseki where a similar position appears as shown in the second diagram.

Second Diagram: This is the joseki for a 3-3 invasion against a star point stone and I only know this:
Black must defend at 1 or white will cut immediately! But thats all the books say. What are the
moves that follow? I can't really figure out the moves here.

In the first example, white's stones are pretty light. Whilst there is some aji, black can't really threaten them, and white doesn't care if a couple of stones drop off because that's just a medium sized endgame move. In this case, white finds it larger to move elsewhere - he doesn't stand to lose too much if he handles the peep at a lightly. On the other hand, black can aim at this group on a large scale, perhaps by attacking a group elsewhere, so adding a move somehow is quite big for white too.

In the second case, black needs to protect or his wall becomes useless. Without the protection move, white can just cut and black is in some trouble already, or the clamp works flawlessly for white (if this big endgame is better). If white cuts and gets away with it, black's thickness is wasted.

Click Here To Show Diagram Code

[go]$$B Moves 13 to 13
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . 3 X O O . . |
$$ | . . . . . . . . . . . . . b 2 X O . . |
$$ | . . . , . . . . . , . . . . . X O . . |
$$ | . . . . . . . . . . . . . . . a X O . |
$$ | . . . . . . . . . . . . . . . . X O . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . c . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

At this point, white has various options depending on the surrounding conditions. There probably will be important conditions, or black would not play this way in the first place.

a and b would be obvious moves to fight. Assuming white has some stones in the area, he would choose one such that some of black's stones will get cut off from the others.

White might also choose c (that is, tenuki, not this specific point on an empty board), leaving the cutting stone as massive aji for black later, for instance if this wall is in a black moyo white can invade in such a way that black must spend moves to capture the cutting stone.

_________________
That which can be destroyed by the truth should be.
--
My (sadly neglected, but not forgotten) project: http://dailyjoseki.com

first diag there is a weakness but possible to tenuki.
i would tenuki for sure. it would be very slow and overconcentrat to cover that weakness and give sente to black at this point of the game. it was a mistake for black to expect white to answer that move.

second diag..is close to must defend weakness.
there is nothing wrong with defending because it is solid and thick.

to daniel_the_smith:
when your opponent has a weakness, it is usually better for you to attack weakness indirectly.
attacking it directly will usually settle their group. you can get more out of that weakness by not attacking.
instead, build more influence elsewhere so they will have to play a move to cover their weakness.

i hope this broaden your view of this game.

_________________
"The more we think we know about
The greater the unknown"
Words by neil peart, music by geddy lee and alex lifeson

Thanks amnal, daniel_the_smith and Magicwand that answers my question.
This question confused me for a while now.

Now a new question: First diagram - in the lower left corner it looks like white messed up a joseki there, is it bad for white?
Black did gain something in the bottom and the left so I think black looks a lot better there.

White has helped black a bit there. The normal joseki (ignoring the shimari, which does affect things) is:

Click Here To Show Diagram Code

[go]$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 8 . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 3 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 2 . 4 . 6 . . . . . . . . . . . |
$$ | . . c , . . . . . , . . . . . , . . . |
$$ | . . a 1 . 5 . 7 . . . . . . . . . . . |
$$ | . d b . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

The numbered stones show a standard joseki for white. The abcd exchange is optional. White will also often exchange a for b, then tenuki and potentially take d later. You can look this position up for more informationon the nuances.

The vital move is white's pincer. Playing on top of black just helps black settle his stone without white getting a base.

This joseki isn't very common for white when black has the shimari, as white's pincer stone may itself be attacked. Having said that, it is fine for white, and has been played by professionals.

A much more common choice for white is:

Click Here To Show Diagram Code

[go]$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . X . . . . . . . . . . . . . . |
$$ | . . X , . . . . . , . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 3 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 2 . . . . . . . . . . . . . . . |
$$ | . . . , . . 4 . . , . . . . . , . . . |
$$ | . . . 1 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

This can lead to some complex variations, but generally helps white settle better, without the vagueness of a pincered pincer.


There are, of course, many other ways to play.

hum...it is about even.
i am thinking white approached high and black pincered and white jumped etc etc..
i would (and most professionals) prefer lower approach because it will leave 3-3 invasion.
but high approach can be played as such.
black gained few points bottom but side two stones are weak and it is a target.

although i prefer black because of high approach, it is about even.

_________________
"The more we think we know about
The greater the unknown"
Words by neil peart, music by geddy lee and alex lifeson

@Magicwand: I assume you're talking about my second diagram?

Click Here To Show Diagram Code

[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . 7 . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 3 . 6 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 2 . 4 . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . 1 . 5 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Click Here To Show Diagram Code

[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 7 . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 3 . 6 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 2 . 4 . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 1 . 5 . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

_________________
We don't know who we are; we don't know where we are.
Each of us woke up one moment and here we were in the darkness.
We're nameless things with no memory; no knowledge of what went before,
No understanding of what is now, no knowledge of what will be.

i think my answer applies to both diag.
not much different.
edit: ic what you mean

either way i think they are about even.

_________________
"The more we think we know about
The greater the unknown"
Words by neil peart, music by geddy lee and alex lifeson

Thanks again, that's all I wanted to know for now.