In this position:

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[go]$$Wc
$$ -----------
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . . . b .
$$ | . . . X . a .
$$ | . . X . . . .
$$ | . c O O . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . X . . .
$$ | . . . . . . .
$$ | . . . . . . .[/go]

I read "'a' is correct, 'b' is not recommended."

Why is 'b' not recommended? Doesn't 'a' leave the corner open for invasion?

Is it because :B: at c will most probably be sente?, making the corner not open for invasion?

(sorry if it's a stupid question)

Black b doesn't put that much pressure on white, while a does so. Also, the corner is open even if black plays b.

But c is the worst. White will just attach and get a nice thick outside shape.

I also struggle with this joseki. What are W's choices after B a? C12/ tenuki / ?

One joseki.

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[go]$$Wc
$$ -----------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . X . X . . .
$$ | . . X . . . 6 . .
$$ | . . O O . . 7 . .
$$ | . . . . . . 3 . 5
$$ | . . . 1 . . . . .
$$ | . . . . . . 4 . 8
$$ | . . 2 X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

It is not a stupid question at all. Many times we see advice, "A is best, B is not as good" without a (sufficiently) clear explanation why.

So what explanation do we have for this?

When Black plays below, White normally answers at or "a". Jumping out to "b" instead has no impact on the top because is high. At the same time "b" leaves White's shape thin with absolutely no eye shape potential yet. The corner remains open to a White invasion at "c" later. On the other hand...

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[go]$$Bc
$$ -----------
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . c . . . .
$$ | . . . X . 1 .
$$ | . . X . . . .
$$ | . . O O . b .
$$ | . . . . . . .
$$ | . . a 2 . . .
$$ | . . . . . . .
$$ | . . . X . . .
$$ | . . . . . . .
$$ | . . . . . . .[/go]

When Black plays , the most common reply for White is with "b" and "c" only 2nd and 3rd. Because Black has played low, White has more room to maneuver and immediately presses Black down somewhat. In addition, White threatens to continue with the sequence of and . This leads to various continuations depending on how Black answers but it is considered a weakness in Black's shape.

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[go]$$Bc
$$ -----------
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . 6 . 5 1 .
$$ | . . . X 4 . .
$$ | . . X . . 2 .
$$ | . . O O . . .
$$ | . . . . . . .
$$ | . . c b . . .
$$ | . . . . . . .
$$ | . . . X . . .
$$ | . . . . . . .
$$ | . . . . . . .[/go]

Note that in professional play, Black plays in 90% of the examples in GoGoD. So, the big guys consider it a no-brainer.

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[go]$$Bc
$$ -----------
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . X . 1 .
$$ | . . X . . . .
$$ | . . O O . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . X . . .
$$ | . . . . . . .
$$ | . . . . . . .[/go]

However, the knight's move comes up often via a different order of moves when White plays an approach to a small knight enclosure as below.

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[go]$$Wc
$$ -----------
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . . . X .
$$ | . . . X . . .
$$ | . . 2 . . 5 .
$$ | . . 1 3 . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . . . 4 . . .
$$ | . . . . . . .
$$ | . . . . . . .[/go]

_________________
Dave Sigaty
"Short-lived are both the praiser and the praised, and rememberer and the remembered..."
- Marcus Aurelius; Meditations, VIII 21

One additional question:

If for any reason [edit] black decided to take the corner... He wouldn't have played the kick in the first place.

Ok, if for any other reason or move order, maybe with w starting at 6-4 or whatever other situation that never happens except when I'm playing and then it happens and I hate myself for not having imagined it before:

Just as an exercise, how would black lock the corner in this position?

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[go]$$Wc
$$ -----------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . b . . . . .
$$ | . . . X . . . . . ,
$$ | . a X . . . . . . .
$$ | . . O O . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]

My ideas are a and b, but I'm not strong enough at L&D to know whether those lock the corner or not.

I don't know if White can really take the corner if Black doesn't defend. But White can get a really nice shape.

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

The next move by Black is very important.

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[go]$$Bc
$$ -----------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . X 1 . . . .
$$ | . . . X O O . . . ,
$$ | . . X . . . . . . .
$$ | . . O O . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]

This is mostly wrong.

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[go]$$Wc
$$ -----------
$$ | . . . . . . . . . .
$$ | . . 4 3 8 9 . . . .
$$ | . . 2 1 X X 7 . . .
$$ | . . 6 X O O . . . ,
$$ | . . X 5 . . . . . .
$$ | . . O O . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]

White can force like that.

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[go]$$Bc
$$ -----------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . X . . . . .
$$ | . . . X O O . . . ,
$$ | . . X 1 . . . . . .
$$ | . . O O . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]

This looks crude, but it's often the correct response.

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[go]$$Wc
$$ -----------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . 2 X . . . . .
$$ | . . . X O O . . . ,
$$ | . . X X . . . . . .
$$ | . . O O . 1 . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]

And White has a nice shape on the outside in Sente and can now take the initiative.


My Kyu-ish insights =)

_________________
My "guide" to become stronger in Go

Which is better for the attack, "a" or "b"?

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

This thread helped in a game today!

Fortunate for me my opponent kicked me twice so I had two corners to wait for an opportunity to attack.

One group I never got the chance to attack.

But the other one i split in two and killed half of it and won the game

Did you mean to write if 'Black' takes the corner? Your text and proposed plays do not seem to match up here.

_________________
Dave Sigaty
"Short-lived are both the praiser and the praised, and rememberer and the remembered..."
- Marcus Aurelius; Meditations, VIII 21

[inline-hide][/inline-hide]

Yes, sorry, i meant black. If black wants to secure the corner will a or b work?

OK!

Write it on Your Heart

Write it on your heart
that every day is the best day in the year.
He is rich who owns the day,
and no one owns the day
who allows it to be invaded with fret and anxiety [about protecting the corners].
Finish every day and be done with it.
You have done what you could.
Some blunders and absurdities, no doubt, crept in [when you were distracted thinking about the corners].
Forget them as soon as you can, tomorrow is a new day;
begin it well and serenely,
with too high a spirit to be cumbered with your old nonsense [about the corner].
This new day is too dear, with its hopes and invitations,
to waste a moment on the yesterdays [hiding in the corners]...

Ralph Waldo Emerson [with a little EZ help]

Write it on your heart - "I DO NOT WANT TO PROTECT THE CORNER!"
Count! From D16 to the upper edge there are 3 lines. From D16 to D10 there are 5 lines. Five is more than three.
"I DO NOT WANT TO PROTECT THE CORNER!"
"I DO NOT WANT TO PROTECT THE CORNER!"
"I DO NOT WANT TO PROTECT THE CORNER!"
[Repeat]

In the position below if you want to protect the corner, you play or "a". Of course you are still exposed at the points marked "b".

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[go]$$Bc
$$ -----------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . b b . . . .
$$ | . a 1 X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . O . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]

Why am I so adamant?
In the position below when Black exchanges for , what happens? (This is not a trivial question and many amateurs do not really understand this exchange.) In any number of books we can read that Black plays the kick to make White heavy. This is true. Black forces White to double the local investment (two stones instead of one) while at the same time cutting off White's slide into the corner. However, the other sign of the coin is that Black strengthens White. The two White stones are stronger than the single stone was before. If Black now turns away (whether to seal the corner or simply to play elsewhere), White will be able to use that strength to press down the top and/or to play against the D10 stone. So once Black plays , HE DOES NOT CHANGE HIS MIND!

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[go]$$Bc
$$ -----------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . 1 . . . . . . .
$$ | . . O 2 . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . X . . . . . ,
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]

In GoGoD there are 639 games with the position below. There is one (count it, ONE) game where Black plays elsewhere, it is a nine-stone teaching game where Black played elsewhere against Go Seigen in 1961 (result W+R of course).

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[go]$$Bc Search Pattern
$$+ - - - - - - - - -
$$| . . . . . . . . .
$$| . . . . . . . . .
$$| . . . . a . . . .
$$| . . . X . . . . .
$$| . . X . . . . . .
$$| . . O O . . . . .
$$| . . . . . . . . .
$$| . . . . . . . . .
$$| . . . . . . . . .
$$| . . . X . . . . .
$$| . . . . . . . . .[/go]

There is also one (yep count it too, ONE) game where Black played your diagonal move at "a" above. I am pleased to report that Maeda Nobuaki paid for his sin at the hands of Hashimoto Utaro (W+R).

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[go]$$Bc Hashimoto Utaro - Maeda Nobuaki East-West Japan match, 1937-11-22~12-22
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | X . X . O O . . . O . . . . 1 . . . . |
$$ | O X X , X X O O . , . . . . . X . . . |
$$ | O O O X . . X O . . . . . . . . X . . |
$$ | . . . . X . X . . . . . . . . O O . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . O O X O . . . . . . . . . . . . . . |
$$ | . X O X X O . . . . . . . . . . 6 . . |
$$ | O O X O X . . . . , . . . 5 . X . . . |
$$ | . X X . . . . . . . . . . . . . 3 7 . |
$$ | . . . . . . . . . . . . . . . 4 2 . . |
$$ | . . X X . . . . . . . . . . . . . . . |
$$ | . X O O X X . . . . . . . . . . . . . |
$$ | . O O X O . . . . . . O . . . 0 9 . . |
$$ | . . . , O . . . . O . . . X . X 8 . . |
$$ | . . . O . . . . . . . X . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

_________________
Dave Sigaty
"Short-lived are both the praiser and the praised, and rememberer and the remembered..."
- Marcus Aurelius; Meditations, VIII 21

how I see it is you kind of protect your corner by pressuring the two white stones.
Because any move white makes against the corner strengthens your stones and makes it harder to survive with the kicked stones.

If Black wants to secure the corner he should just shoot himself.

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

You do sometimes see this, in special circumstances.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.