Invading the corner

bleep · #1

I've just started reading a book on the opening, and it tells me that invading the corner is the standard answer to the pincer (Opening Theory made Easy). That makes sense, but the problem I have is reconciling that to invading the corner early, which I've always believed to be a poor choice. Don't the two ideas directly contradict each other, and if that's the case, what makes it suddenly ok to leap into the corner early in the game?

lorill · #2

bleep wrote:

I've just started reading a book on the opening, and it tells me that invading the corner is the standard answer to the pincer (Opening Theory made Easy). That makes sense, but the problem I have is reconciling that to invading the corner early, which I've always believed to be a poor choice. Don't the two ideas directly contradict each other, and if that's the case, what makes it suddenly ok to leap into the corner early in the game?

Well, on one case, you have already approached, on the other you want to invade without approaching.
That's the difference.

Twitchy Go · #3

Click Here To Show Diagram Code: [go]$$Wcm42 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O O X . . . . . . . . . . . . . . | $$ | . . O X . X . . . . . . . O . O O O . | $$ | . . O X . . . . . , . . . . X X X O . | $$ | . O X . . . . . . . . . . . . . X X . | $$ | . O X . . . . . . . . . . . . X O . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Both of these sequences end in gote for black. The left side is a 33 invasion, and the right is diving into the corner after a low 1space pincer. On the left black gets a bigger wall and seals white into the corner, that group isn't going to effect the rest of the game much. On the right blacks wall is smaller and white is out on the side. Can you see how the approach move helps white get a better result then if he just invaded the 33?
I'm not sure if this completely answers your question, but it is at least part of the answer.

Boidhre · #4

Mostly posting this to see how wrong my reasoning is: The answer on whether you go straight to 3,3 or jump out depends on the rest of the board. Will "black's" resulting wall work well or not, and similar concerns. If black pincers, then they are happy to trade the corner for an outside wall or the pincer stone is acting as an extension off some other group of stones and they are happy with whatever you do or with a tight pincer and favourable conditions for a wall making invasion unattractive they are trying to create a weak group to attack for profit.

This is my understanding of pincers, when to use them and how to respond. It's undoubtedly imperfect and flawed of course.

Bill Spight · #5

Click Here To Show Diagram Code: [go]$$Wcm42 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O O X . . . . . . . . . . . . . . | $$ | . . O X . X . . . . . . . O . O O O . | $$ | . . O X . . . . . , . . . . X X X O . | $$ | . O X . . . . . . . . . . . . . X X . | $$ | . O X . . . . . . . . . . . . B O . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

This is a better comparison. With the one space pincer, the :bc:

stone is questionable. With the three space pincer it is correct.

kvasir · #6

Click Here To Show Diagram Code: [go]$$Wcm42 $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . Q X . . . . . . . . . . . . . . . . | $$ | . O X . . . . . . . . . . . . . . . . | $$ | . . O X . . . . . , . . . . . , . . . | $$ | . . O X . X . . . . . . . . . . . . . | $$ | . . O O X . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Click Here To Show Diagram Code: [go]$$Wcm42 $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . @ . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . O X . . . . . , . . . . . , . . . | $$ | . . O X X O . X . . . . . . . . . . . | $$ | . . O O X . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

The most important difference between these diagrams is that the white marked stone is ahead of black's wall in one and not the other. Another difference is that black's group in the second diagram is also not that thick. Black usually takes sente anyway.

The same thing about the white marked stone being ahead of black's wall applies to this joseki as well.

Click Here To Show Diagram Code: [go]$$Wcm42 $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . @ . . . . . . . . . . . . . . . . | $$ | . . . X . . . . . . . . . . . . . . . | $$ | . . O X . X . . . , . . . . . , . . . | $$ | . . O X X O . . . X . . . . . . . . . | $$ | . . O O X . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

txcpa · #7

Twitchy Go wrote:

Click Here To Show Diagram Code: [go]$$Wcm42 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O O X . . . . . . . . . . . . . . | $$ | . . O X . X . . . . . . . O . O O O . | $$ | . . O X . . . . . , . . . . X X X O . | $$ | . O X . . . . . . . . . . . . . X X . | $$ | . O X . . . . . . . . . . . . X O . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

Both of these sequences end in gote for black. The left side is a 33 invasion, and the right is diving into the corner after a low 1space pincer. On the left black gets a bigger wall and seals white into the corner, that group isn't going to effect the rest of the game much. On the right blacks wall is smaller and white is out on the side. Can you see how the approach move helps white get a better result then if he just invaded the 33?
I'm not sure if this completely answers your question, but it is at least part of the answer.

Excuse my ignorance, but would someone mind posting the sequence for the right-side group? Thanks!!

bleep · #8

Great, thanks for the many replies.

Seeing them side by side made it quite clear, so that cleared it up pretty easily.

Still not sure how to post a sequenced diagram, otherwise I'd gladly show you, but the situation arises when black pincers the white approach stone, and white then invades on the 3,3.

Dusk Eagle · #9

txpca wrote:

Excuse my ignorance, but would someone mind posting the sequence for the right-side group? Thanks!!

Click Here To Show Diagram Code: [go]$$Bcm1 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . , . . . . . . . . . . . . 6 4 0 . | $$ | . . . . . . . . . , . . . . 7 1 5 8 . | $$ | . . . . . . . . . . . . . . . . . 9 . | $$ | . . . . . . . . . . . . . . . . 2 . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . 3 . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code: [go]$$Bcm11 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . , . . . . . . . . . . 2 . O O O . | $$ | . . . . . . . . . , . . . . X X X O . | $$ | . . . . . . . . . . . . . . . . 1 X . | $$ | . . . . . . . . . . . . . . . . O . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . |[/go]

As for why black extends at move 7 instead of playing a hane, go to http://eidogo.com and enter the above sequence.

Bill Spight · **#10**

Click Here To Show Diagram Code: [go]$$Wc $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . O O X . . . . . . . . . . . . . . | $$ | . . O X . X . . . . . . . 9 . 3 1 7 . | $$ | . . O X . . . . . , . . . . 4 X 2 5 . | $$ | . O X . . . . . . . . . . . . . 8 6 . | $$ | . O X . . . . . . . . . . . . 0 W . . | $$ | . . X . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , B . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

On the right, you already have a White approach, :wc:

, and a Black pincer, :bc:

. Then

invades the corner.

Uberdude · **#11**

bleep wrote:

but the problem I have is reconciling that to invading the corner early, which I've always believed to be a poor choice.

Don't let this idea stop you playing 3-3. Something I noticed as I got stronger was invading at 3-3 was a good move earlier than I expected. For example if a 4-4 has 2 low far extensions then 3-3 is often good (of course you need to look at the whole board but just in this quadrant 3-3 is good). This surprised me as a beginner having learnt the "Don't 3-3 invade under a 4-4 right away" idea, but the point is if black follows the standard sequence you get an alive group with a decent amount of territory in sente, and one of black's extensions ends up misplaced. This also applies with high extensions but to a somewhat lesser extent. If you don't 3-3 and black gets to add a move to the corner then it is much less easy to break the framework: of course you can invade and live but you will have a weak group and weak groups are bad. The brilliance of the 3-3 is it is not a weak group and you often even get sente!

Click Here To Show Diagram Code: [go]$$Wcm1 $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . X . . . . . . 1 . . | $$ | . . . , . . . . . , . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

A whole board position I was studying recently where an "early" 3-3 is fine:

Click Here To Show Diagram Code: [go]$$Wcm6 Chinese opening continuation $$ --------------------------------------- $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . 2 . . . . . . . . . . 5 . . | $$ | . . . O . . . . . 4 . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . 3 . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . , . . . . . , . . . . . , . . . | $$ | . . . . . . . . . . . . . . . . X . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . O . . . . . , . . . . . , . . . | $$ | . . . . . 1 . . . . . . . . . X . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ | . . . . . . . . . . . . . . . . . . . | $$ ---------------------------------------[/go]

For more, see this post and the subsequent one.

Joaz Banbeck · **#12**

bleep wrote:

I've just started reading a book on the opening, and it tells me that invading the corner is the standard answer to the pincer (Opening Theory made Easy). That makes sense, but the problem I have is reconciling that to invading the corner early, which I've always believed to be a poor choice. Don't the two ideas directly contradict each other, and if that's the case, what makes it suddenly ok to leap into the corner early in the game?

Despite his self-deprecating comments that accompany the following...

Boidhre wrote:

...The answer on whether you go straight to 3,3 or jump out depends on the rest of the board...

...Boidhre has the essential idea correctly. Unfortunately, defining and interpreting 'the rest of the board' is often a complicated proposition.

I'm going to make a superficial pass at that that huge task.

As a preliminary matter, let us remember that 'invading the corner' is often a misnomer. A 4-4 stone does not own the corner. It is not his, therefore you can't invade it.
I'd prefer to phrase it as 'taking the corner'. When the opponent has a 4-4 stone, taking the corner is something you can do, and it is also something that he can do, because - despite that 4-4 stone - nobody has done it yet.

As a second preliminary matter, let us recall that pros tell us that a wall is generally worth about 2.5 to 3 points per stone, so that in a situation like this:

Click Here To Show Diagram Code: [go]Bc $$ | . . . . . . . . . . . . . . . . . . $$ | . . . X X X X . , . . . . . , . . . $$ | . . . O O O O . . . . . . . . . . . $$ | . . . . . . . . . . . . . . . . . . $$ | . . . . . . . . . . . . . . . . . . $$ ---------------------------------------[/go]

...white is getting 2 points of territory per stone, thus black is showing a net profit of 1/2 to 1 points per stone by playing on the fourth line.

1) With the preliminaries out of the way, let us look at the simplest example, the 'invasion' of the lone 4-4 stone:

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . , . . . . . , . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . , . . $$ | . . W . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

Black can make a wall with :b1:

, which threatens to kill the white stone, so white replies with :w2:

. Black is showing a net profit here already. Next he can hane, which forces white down one row, making black's net profit about 1.5 to 2 points per stone. White makes a slight change of direction to ensure eye space with 4 thru 7, then continues with 8, 9, and 10, and black finishes with 'a'. ( This is the simplest variation. There are more complex variations, but let's stick to the natural play for the sake of example. )

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . , . . . . . , . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . 7 . . . . . . . . . $$ | . 5 . . . . . . . . . . $$ | . 4 1 X . . . . . , . . $$ | . 6 W 2 3 9 a . . . . . $$ | . . . . 8 0 . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

If the rest of the quadrant is empty as shown in this example, this is a net profit of something like 7 points for black. ( :b1:

and

are partially masked by their neighbors, so they count a bit less, whereas 'a' is worth a bit more because of it's influence in two directions. Counting exactly is hard, but I seem to recall a pro saying about 7 points. )

In short, this is a bad play for white because black gets more in influence than white gets in territory.

To underline the point, let's look at a slightly contrived counter example:

Click Here To Show Diagram Code: [go]$$Bc $$ | . . O . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . , . . . . . , . . $$ | . . O . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . O . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . , . . $$ | . . W . . . . . O . . O $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

Here, white can take the corner territory at a net profit, for black's influence is nearly neutralized by the nearby white stones.

Click Here To Show Diagram Code: [go]$$Bc $$ | . . O . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . , . . . . . , . . $$ | . . O . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . X . . . O . . . . . $$ | . X . . . . . . . . . . $$ | . O X X . . . . . , . . $$ | . O O O X X X . O . . O $$ | . . . . O O . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

In the resulting situation, white does very well. Indeed, black may have to struggle just to live.

2) Next is the 4-4 stone with 2 extensions:

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . , . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . c . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . d . X . . . . . X . . $$ | . . a . . . b . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

There are three general areas to invade in black's framework: the corner 'a', and two sides 'b' and 'c'. ( There are also hybrids like 'd', part corner, part side, but in practice they tend to resolve to one or the other. )

The problem with a side invasion...

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . , . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . 8 . . . . . $$ | . . . 3 . . . . . 9 . . $$ | . . . . . . . . . . . . $$ | . . . X . 2 . 4 . X . . $$ | . . . . 1 W . 6 5 . . . $$ | . . . . 7 . . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

...is that with rather simple moves, black can chase white and secure both the corner and some of the other side. And white is still not clearly alive. ( These may not be best moves by both sides. They just illustrate the general nature of the position )

By contrast, the corner invasion is absolutely alive.

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . , . . $$ | . . . . a . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . X . . . . . . . . . $$ | . X . . . . . b . . . . $$ | . O X X . . . . . X . . $$ | . O O O X X X . . . . . $$ | . . . . O O . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

...and there are still invasions or reductions of the sides with moves like 'a' or 'b'.

Again, the benefits of an invasion are apparent when contrasted with a diagram in which black gets the 3-3 first:

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . , . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . c . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . X . . $$ | . . X . . . b . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

Now the corner is out of reach, and even the side invasions can be attacked vigorously.

This is all just my attempt to knit together bits and pieces of theory that I've picked up here and there. I'll leave it out here to be critiqued by stronger players. If they don't trash it entirely, I'll come back after lunch and continue.

Buri · **#13**

Greetings,
an interesting tip I learnt from the Guo Juan Internet school.
If your opponent has a stone on the star point and two low wings IE stones on either side on the points below the star points then a 3-3 invasion is urgent.
Best wishes,
Buri

EdLee · **#14**

Joaz Banbeck wrote:

A 4-4 stone does not own the corner. It is not his, therefore you can't invade it.

Joaz, seems you got this backwards. It is precisely because something is not already solid territory
(that is, it does not already belong 100% to your opponent), that you can invade it.
If an area is already 100% your opponent's, you cannot invade it -- you'll simply die inside.
For example, if your opponent already has both 4-4 and 3-3, how can you invade 3-3 now?

Joaz Banbeck · **#15**

EdLee wrote:

Joaz Banbeck wrote:

A 4-4 stone does not own the corner. It is not his, therefore you can't invade it.

Joaz, seems you got this backwards. It is precisely because something is not already solid territory
(that is, it does not already belong 100% to your opponent), that you can invade it.
If an area is already 100% your opponent's, you cannot invade it -- you'll simply die inside.
For example, if your opponent already has both 4-4 and 3-3, how can you invade 3-3 now?

I meant what I said.

What I'm trying to emphasize - which beginners often miss - is that the 4-4 stone has 0% of the corner. You can take the corner, but that taking should not be called an invasion.
IMHO, he proper use of the word 'invade' should be used for that which someone already has, or at least partially has.

Uberdude · **#16**

Joaz Banbeck wrote:

Black can make a wall with :b1:

, which threatens to kill the white stone, so white replies with :w2:

. Black is showing a net profit here already. Next he can hane, which forces white down one row, making black's net profit about 1.5 to 2 points per stone. White makes a slight change of direction to ensure eye space with 4 thru 7, then continues with 8, 9, and 10, and black finishes with 'a'. ( This is the simplest variation. There are more complex variations, but let's stick to the natural play for the sake of example. )

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . , . . . . . , . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . 7 . . . . . . . . . $$ | . 5 . . . . . . . . . . $$ | . 4 1 X b . . . . , . . $$ | . 6 W 2 3 9 a . . . . . $$ | . . . . 8 0 . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

This is a huge mistake for white, and shows the dangers of blindly memorizing the end position of josekis rather than thinking about your moves as you play them. 4 should be played at 8. Playing at 4 immediately is a big mistake in order as black should not make the hanging connection at 7 but rather solid connect at b. Then white can only make a sealed in L+2 group in gote (but with a clamp aji on 5) which is far inferior to the joseki result of a non-sealed in group in sente.

Joaz Banbeck wrote:

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . , . . $$ | . . . . a . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . X . . . . . . . . . $$ | . X . . . . . b . . . . $$ | . O X X . . . . . X . . $$ | . O O O X X X . . . . . $$ | . . . . O O . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

...and there are still invasions or reductions of the sides with moves like 'a' or 'b'.

Err, what? 'a' or 'b' both look fairly unlikely to be good moves and far too close to black's strong group, likely creating heavy groups. Usually you just give black that territory and try to make him depressed from being overconcentrated.

Joaz Banbeck wrote:

Again, the benefits of an invasion are apparent when contrasted with a diagram in which black gets the 3-3 first:

Click Here To Show Diagram Code: [go]$$Bc $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . , . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . c . . . . . . . . $$ | . . . a . . . . . . . . $$ | . . . . . . . . . . . . $$ | . . . X . . . . . X . . $$ | . . X . . . b . . . . . $$ | . . . . . . . . . . . . $$ | . . . . . . . . . . . . $$ ----------------------------[/go]

Now the corner is out of reach, and even the side invasions can be attacked vigorously.

Adding a move at 3-3 is one possiblity, but more normal would be to add a one point jump at a (and which side you pick depends on the rest of the board).

P.S. I call it an invasion, as do many others (including pros).

EdLee · **#17**

Joaz Banbeck wrote:

which beginners often miss - is that the 4-4 stone has 0% of the corner.

This depends entirely on how you define "the corner". In the opening, we usually consider "taking an empty corner"
to include various moves like 3-4, 3-3, 3-5, 4-5, and 4-4.

I would say the 4-4 has SOME prescence in the corner.

PS. I agree many beginners (including myself) at first would misunderstand the 4-4
to mean owning a significant chunk of the corner.

EdLee · **#18**

Uberdude wrote:

P.S. I call it an invasion, as do many others (including pros).

Actually, this is an interesting point. In Chinese and Japanese, I'm not sure they use "invade" for the above 3-3 placements, do they?
(No idea about in Korean... Kirby?)

oren · **#19**

In　Japanese, it's 打ち込み, uchikomi. While it's not directly invade, I think "invade" is ok to use. "Playing inside" would be more literal.

Shaddy · **#20**

In chinese, the verb used with the 3-3 invasion is dian3, which I don't think translates to 'invade'

Invading the corner

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