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 they may attempt to kill the invading stone outright.

Table of contents Table of diagrams
Standard joseki 1: immediate ko
Standard joseki 2: push first
Standard joseki 3: White connects
Standard joseki 2: Black ignores the ko
Standard joseki 1: Black ignores the ko (1-5)
Standard joseki 1: Black ignores the ko (4-3)
Killing outright (4-2)
Killing outright (1-3)
Diagonal move at W3
Solid connection at W5, i
Solid connection at W5, ko, i
Solid connection at W5, ko, ii
Reference
Solid connection at W5, Black tries to kill
Solid connection at W5, Black tries to kill, White cuts
Solid connection at W5, Black tries to kill, White clamps
Solid connection at W5, Black tries to kill, overplay
2-2 Placement
2-2 Placement – continuation
2-2 Placement – Black tries to save corner stone.
2-2 Placement – Black tries to kill, one possibility

Charles Matthews has a [ext] commentary on GoBase on the kos in this joseki (which he calls ‘apex kos’) as part of his series on [ext] Setpiece Kos. He pays careful attention to the overall context of the game and Black’s outside strength.

Standard josekis

[Diagram]
Standard joseki 1: immediate ko  

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.

[Diagram]
Standard joseki 2: push first  

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: White connects  

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 has 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 considered a concession to White. However, W2 to W6 lives unconditionally.

[Diagram]
Standard joseki 1: Black ignores the ko (1-5)  

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 (4-3)  

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

Black 6 at 4-2

[Diagram]
Killing outright (4-2)  

If B6 and B8 kill outright, then usually White can cut at W9. Without additional supporting Black stones, Black would be in serious trouble. If circumstances does not allow W9, then a possible alternative is a.

Also note that if B8 is played at b, then White lives at c.



Black 6: Placement (1-3)

[Diagram]
Killing outright (1-3)  

Black can also attempt to kill outright with the placement at B6. Here W7 is a possible reply, and if Black continues with a then White can push at b as before.



Alternatives for White 3

Diagonal move at 4-2

[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).



Solid connection

[Diagram]
Solid connection at W5, i  

This situation should not be confused with 4-4 point, low approach, low extension, 3-3 invasion: the solid connection at W5 is not the normal move here. W5 is usually inferior to directly starting a ko at a. Depending on circumstances, Black can choose to to make ko at b or go for the kill at c.


Ko

[Diagram]
Solid connection at W5, ko, i  

One of the simplest Black responses 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 as the descent at b, then the placement at c kills the corner unconditionally.

[Diagram]
Solid connection at W5, ko, ii  

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

Although White takes the ko first, there is a distinct disadvantage for her if she wins it by capturing at a: it does not threaten any outside Black stones. Compare that with the standard joseki in the following diagram.

[Diagram]
Reference  

In the standard josekis (with or without the white+circleblack+circle exchange), when White wins the ko, she captures at W1, seriously threatening Black’s left side unless he defends at a.

Black goes for the kill, with cut aji

[Diagram]
Solid connection at W5, Black tries to kill  

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, Black tries to kill, White cuts  

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, Black tries to kill, White clamps  

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, Black tries to kill, overplay  

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

Black 4 at 2-2

[Diagram]
2-2 Placement  

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

[Diagram]
2-2 Placement – continuation  

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]
2-2 Placement – 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]
2-2 Placement – Black tries to kill, one possibility  

Matlock?: The 2-2 point response appears twice in Waltheri's go pattern search (as of 2015-03-19). In one case White’s 3-3 invasion looked like a mistake, as she invaded a strong position where Black’s response actually worked and White could not escape. In the other case, White was able to make life in the corner.



See also

  • 4-4 6-3 enclosure – The context for this invasion
  • BQM 104 – An failed attempt to live unconditionally
    Unconditional life?
  • BQM 180 – A failed attempt to start a more favourable ko
    Better ko?

4-4 6-3 enclosure, 3-3 invasion last edited by PJTraill on February 17, 2019 - 17:38
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