4-4 6-3 enclosure, 3-3 invasion

    Keywords: MiddleGame, Joseki

In ordinary circumstances, invading the 3-3 point in a 4-4 6-3 enclosure leads to ko for life. However, if the player with the enclosure has strong supporting stones outside, then he or she may attempt to kill the invading stone outright.

Table of contents

Standard josekis

[Diagram]
Standard joseki 1  

There are two standard josekis for the 3-3 invasion, both leading to ko for life. If White wins this ko, then White captures at a, which can cause considerable damage to Black's position.

Charles Matthews has a [ext] commentary on GoBase on this joseki.

[Diagram]
Standard joseki 2  

White can also interchange W3 with B4 before starting the ko. But beware of the possibility of B4 playing at a.

[Diagram]
Standard joseki 3  

If white is already thick outside, she can also consider playing W9 here. Assuming Black has to protect his cut with B10, White lives unconditionally. Black is very thick and has sente, but White managed to destroy all the points in the corner.


Black ignores the ko

[Diagram]
Standard joseki 2: Black ignores the ko  

If Black cannot win the ko, then B1 can minimize the damage, but it must be a concession to White. However, W2 to W6 lives unconditionally.

[Diagram]
Standard joseki 1: Black ignores the ko  

For standard joseki 1, a Black concession at B1 can be answered by W2 or a. Which is the better move depends on the surrounding stones. In practice it would be hard to kill the corner after W2: White must have many local ko threats such as b. Black would quite like to exchange Black c for White d, to relieve shortage of liberties around the cutting point at e - but this also helps White form eyes.

[Diagram]
Standard joseki 1: Black ignores the ko  

Another way Black can ignore the ko is to play at B1 instead. After the W2 and B3 exchange, White can fix the corner and live unconditionally, but often White can simply tenuki because Black can only kill the corner through a ko - something that Black had originally avoided in the first place.



Black tries to kill outright

[Diagram]
Killing outright  

If B1 and B3 kills outright, then usually White can cut at W4. Without additional supporting Black stones, Black would be in serious trouble. If circumstances does not allow W4, then a possible alternative is a.

Also note that if B3 is played at b, then White lives at c.

[Diagram]
Killing outright  

Black can also attempt to kill outright by making the placement at B1. Here W2 is a possible reply, and if Black continues with a then White can push at b as before.



Other White plays

[Diagram]
Diagonal move at W3  

In some cases, it may also be possible to play at the diagonal move at W3. This move emphasizes the subsequent attachment at a, particularly if there is a White stone at circle. Possible Black responses include b (attempting to revert to ko), c (emphasizing the subsequent jump into the corner at d), and e (allowing White to live unconditionally but in a low position and possibly hurting the White stone at circle, if any).

[Diagram]
Solid connection at W5  

This situation is not to be mistaken with 4-4 point, low approach, low extension, 3-3 invasion, the solid connection at W5 here is not the normal move. W5 is usually inferior to directly starting a ko at a. Depending in circumstances, Black can choose to respond at b or c.

[Diagram]
Solid connection at W5  

One of the simplest Black response is to simply bend at B6, but this simple move is also solid because it implicitly protects against the cutting point at a. White still can make a ko with W7 and W9. If W9 is played at the descent at b, then the placement at c kills the corner unconditionally.

[Diagram]
Solid connection at W5  

White takes the ko first at W15. For more details on this standard corner pattern, see tripod group with extra leg.

Although White takes the ko first, there is a distinct disadvantage for White if White wins the ko by capturing at a. Note that winning this ko does not threatening any outside Black stones.

[Diagram]
Reference  

Compare the above diagram with the ko in the standard josekis, either with or without the White a and Black b exchange. When White wins the ko in any the standard josekis, White captures at W1, seriously threatening Black's left side unless Black defends at c.

Locally dead, with cut aji

[Diagram]
Solid connection at W5  

Another possible Black response is to jump down at B6, giving sufficient space for White to make only one eye in the corner. Typically W7 will push and B8 will block, and White can now choose to cut at a or clamp at b. Whether any of these moves will work out for either player will often hinge on the surrounding stones; without any supporting stones the result is often unfavourable for White.

[Diagram]
Solid connection at W5  

If W9 cuts, B10 is the only move. Subsequently, White may start a possibly large scale fight by pressing down at a, with the result heavily hinging on the surrounding stones. When there are no support stones around, it is sufficient for Black to play at b, and White cannot get a good result because locally the corner is dead. In the absence of supporting stones, W11 playing at c, Black d, White b to push Black low is unreasonable; Black a can push through.

[Diagram]
Solid connection at W5  

White can also clamp at W9. This variation will typically be unfavourable for White because White's position will be low. However, Black has to watch out for the cutting point at a.

In any case, if White ends up in this position, White would be crawling along the second line. Repeated playing of this variation would allow the White player to get strong at crawl. White would be better off playing the 4-4 6-3 enclosure, 2-4 approach rather than the 3-3 invasion.

[Diagram]
Solid connection at W5  

Descending at B10 to separate the W9 stone is an overplay. After W11 and W13, a and b are miai so Black's position collapses.



Discussion

[Diagram]
2-2 Placement  

kb: An interesting counter to the 3-3 showed up in one of my games.

[Diagram]
Placement  

kb: In my game, I continued with W5, giving up the corner for the side (I had a little bit of strength on the left side to support these stones). My question, though, is what is the best way to continue locally in this situation (assuming Black has strength first in one direction, the other, both, and neither)? I didn't find any matches in Gobase.

[Diagram]
Response: Black tries to save corner stone.  

Matlock?: I think this is a mistake for black. White can get a similar but much better result (or life in the corner if black blocks on the outside).

[Diagram]
Response: Black tries to kill, one possible continuation.  

Matlock?: The 2-2 point response appears twice on ps.waltheri.net. Once it looked like white's 3-3 invasion was a mistake, as he invaded into a strong position where black's response actually worked and white could not escape. In the other, the player was able to make life in the corner.



See also


4-4 6-3 enclosure, 3-3 invasion last edited by Timm on March 27, 2015 - 16:01
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