5

This is from an OGS game I (white, 21k) played against a 20k, specifically my move 26. I'm not even sure about white 24, but I definitely think white 26 was a mistake (although it worked out, but only because my opponent made a mistake later):

$$m23
$$ +---------------------------+
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . O . . . . O O X . . |
$$ | . . . . . . . O X X . . . |
$$ | . . . . . . . . O X X . . |
$$ | . . . . . . , . O O X . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . . . 3 . . O X . . . |
$$ | . . . , . . 4 . X , . . . |
$$ | . . . 2 . 1 . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ +---------------------------+

Given my huge wall, my theoretical understanding is that I should use it to drive my opponent into it (which white 26 doesn't seem to do at all), but I'm not sure how I would do that in practice.

The best variation I could come up with when reviewing the game was this:

$$m23
$$ +---------------------------+
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . O . . . . O O X . . |
$$ | . . . . . . . O X X . . . |
$$ | . . . . . . . . O X X . . |
$$ | . . . . . 6 8 . O O X . . |
$$ | . . . . 4 5 7 0 O X . . . |
$$ | . . . . . 3 . 9 O X . . . |
$$ | . . . , . . . . X , . . . |
$$ | . . . 2 . 1 . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ +---------------------------+

(black 29 looks ugly to me, but I don't think black can hane at 30 because a white cut at 29 has all the ladders favoring white?).

But even this result seems pretty good for black to me in the face of the white wall.

Revising the earlier move 24, maybe this might have been a little better:

$$m23
$$ +---------------------------+
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . O . . . . O O X . . |
$$ | . . . . . . . O X X . . . |
$$ | . . . . . . . . O X X . . |
$$ | . . . . . . , . O O X . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . . . . . . O X . . . |
$$ | . . . , 4 . . 2 X , . . . |
$$ | . . . 6 5 1 . 3 . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ +---------------------------+

but I'm not sure black even has to respond to this white 24 because if black grabs the bottom left corner (which my original 24 was trying to prevent), I think they wouldn't be too worried about the cut?

How should white respond to black 23?

8

The biggest strength of a wall is that it keeps your opponents stones from connecting to anything on the other side of it; this forces him to worry about living in general, either by making life independently or connecting somewhere else. This is the general idea behind driving your opponent into your wall: Keep harassing him to keep him worrying about living at all, while you strengthen your own position.

The problem with the situation in OP is that the white wall is poorly positioned to do anything about B23. You can roughly visualize the influence of a wall as extending directly in whatever direction the wall is facing:

$$m23
$$ +---------------------------+
$$ | . . . . . . . . . . . . . |
$$ | . . . . x x x x O X . . . |
$$ | . . x x x x x x O X . . . |
$$ | . x x O x x x x O O X . . |
$$ | . x x x x x x O X X . . . |
$$ | . x x x x x x x O X X . . |
$$ | . x x x x x x x O O X . . |
$$ | . . x x x x x x O X . . . |
$$ | . . . . x x x x O X . . . |
$$ | . . . . . . . . X , . . . |
$$ | . . . 2 . 1 . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ +---------------------------+

As you can see, the main problem with using your wall to attack B23 is that B23 is well outside of your wall's influence. Black can just as easily connect with his stones on the right as he can jump into the lower left corner; either way, he's really not all that worried about living. The wall really doesn't come into play yet.

Playing at W24 as you did isn't really a bad move since it's a big point and restricts black's options — I probably would've done the same myself: Wall or not, a free corner is still a free corner — but he's still not all that worried about living because he can easily connect. Black's jump at B25 was okay but I feel it's a bit of a wishy-washy response here; he can afford to be aggressive, so he probably could've tried to attack the corner directly with b or c:

$$m23
$$ | . . . . . . . . O X
$$ | . . c . . 3 . . O X
$$ | . . . b . . 4 . X ,
$$ | . . . 2 . 1 . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ +--------------------

On the other hand, W26 as original played is problematic because it's working at cross purposes: It's effectively forcing black to strengthen his position, and pushes him into your weak corner. It's also just outside of the influence of your own wall so not very effective at cutting black off from his strength; it's just as easy (if not easier) for black to cut it off from yours. Rather than using your wall to fight, you're basically helping him build his own wall and driving yourself into it instead.

Merits of jumping into the corner aside, if you really wanted to bring your wall into play, the corner isn't how you'd do it here. Letting black establish a base on the bottom means that when he does decide to extend into your walls influence, he's doing so from a position of strength instead of weakness. This severely limits your ability to harass him.

Your second variant, for example, does effectively use the wall to curtail black's invasion (although I believe the black hane at 30 can work by threatening the weak point a in white's wall, I don't have time to really explore that variation). However, this sort of close fighting ends up strengthening black more than it does white, and in the end it really doesn't do anything to secure the corner, which is now really looking rather vulnerable to a black attack around b or c:

$$m23
$$ | . . . . . . . O X X . . . |
$$ | . . . . . . . a O X X . . |
$$ | . . . . . 6 8 . O O X . . |
$$ | . . . . 4 5 7 0 O X . . . |
$$ | . . . . . 3 . 9 O X . . . |
$$ | . . c b . . . . X , . . . |
$$ | . . . 2 . 1 . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ +---------------------------+

In other words, the original corner play at W24 looks wasted; if it doesn't really help your fight, and you're not really trying to defend it, it's just not doing much of anything at all. You'd probably have been better off playing W24 at B25 instead, which lets you bring the wall's influence into play before black has a chance to build up his strength. This would keep him effectively constrained, while also leaving white with a generally stronger position:

$$m23
$$ | . . . . . . . O X X . . . |
$$ | . . . . . . . . O X X . . |
$$ | . . . . . , . . O O X . . |
$$ | . . . 6 . . . . O X . . . |
$$ | . . 5 4 . 2 . . O X . . . |
$$ | . . . 3 . . . 8 X , . . . |
$$ | . . 7 . . 1 . 0 9 . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ +---------------------------+

Your final variant where you extend your wall to cut black off from his strength on the right entirely is the right idea, although if I were black, I'd probably grab the big empty corner before worrying about the connection at a. This really isn't a problem since there's pretty much always going to be a tradeoff between "territory" and "influence"; the first two variants fell into disarray because white was effectively trying to go for both but couldn't really commit to either.

$$m23
$$ | . x x x x x x x O X X . . |
$$ | . x x x x x x x O O X . . |
$$ | . x x x x x x x O X . . . |
$$ | . . x x x x x x O X . . . |
$$ | . . . 3 x x x 2 X , . . . |
$$ | . . . . . 1 . a . . . . . |
$$ | . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . |
$$ +---------------------------+

Whether black chooses to grab the corner or to connect, this lets white play pretty much anywhere within the wall's now larger area of influence to keep black low on the bottom while simultaneously building a huge framework in the top and left, which will make it way harder for black to extend anywhere beyond the corner you let him have (which was already outside of your influence anyway).

Unlike the previous variation, in which white can cap and constrain black while still keeping things relatively civilised, by extending the influence of white's wall before picking any fights white can afford to be a lot more aggressive here and attack the corner without mercy. Splitting black's forces by descending into a (assuming black lets you) will simultaneously threaten his large corner on the right as well increase your wall's left-facing influence, and if you can undercut black's eyespace in the corner (big if), then you can turn this into a straight-up "drive your opponent into your wall" situation. A word of caution though: This can get messy, you probably don't want to try this unless you're really confident in your fighting ability (and/or just thrive on chaos).

In conclusion, two points to keep in mind:

  • Faster is better: If you want to bring your wall's influence into play, you want to do it before black has an opportunity to build up his strength. Spending that one extra turn claiming a corner you don't want to keep while black builds a base can make all the difference here.
  • Choose your battles: Recognize the areas of influence and pick your attacks accordingly; white's influence in the above examples is absolutely terrible for a direct attack on B23, but excellent for capping and restraining it. Relatedly, black will have a far easier time attacking the corner where white has little-to-no influence than white will have defending it. If you are going to attack directly, do so from a position of strength.

But seriously, that all still seems like a lot of work for not so significant an advantage compared to "Hey, look! Free corner!"

  • Great analysis, thank you so much. And good point about the hane (B29 at W30) possibly exploiting the weakness in the wall, I missed that. – balpha Jul 8 '17 at 7:51
4

Your last try is the correct one. You must hane at 24 against the loose Black stone. When Black plays 25, you cut one stone to its right, atariing, the hanging stone, followed by an atari diagonally from 24, and an extension from that atari stone. Your goal is to break up Black's lower side formation, giving you a "flanking" position to both the bottom left and bottom right.

The best way to make use of your wall is to protect it. In the earlier examples, you let Black outflank your wall, greatly reducing its value.

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