3-4 Approaches - the 4-4 Attachment

The directional bias of 3-4 approaches

Barring an urgent local situation, approaching an unenclosed 3-4 point is almost always one of the biggest moves on the board, an idea which AI analysis has only reinforced. As such it is essential for every baduk player to learn at least some portion of the myriad 3-4 approach jōseki, with the one-space low and high approaches being standard elements of every player’s repertoire. Some standard continuations from these approaches are given in the above diagram.

However, the standard approaches do suffer from two major flaws which you need to be aware of in high-level play. The first is that typical approaches to the 3-4 point are inherently directionally biased. Unlike the 4-4 point, there is no symmetry axis with a 3-4 point. As such, the approacher in most relatively peaceful 3-4 point jōseki has a tendency to gravitate away from the side with the original 3-4 stone, as is the case for White in the two examples in the diagram. If we assume that the direction of play in the diagram is the bottom side, then it can be difficult for White to get stones in that direction starting from a high approach without giving up too much locally, especially if Black is also contesting this direction of play. As for the low approach, getting stones on the bottom side in a natural way is nearly impossible using standard methods.

The second problem is that most approaches to the 3-4 point are not necessarily sente. Although in most early opening scenarios one should respond to a 3-4 approach, it is not uncommon for there to be a sufficiently important play on the board that overturns this heuristic. Part of this is that ignoring a standard 3-4 approach is not all that dangerous locally. With the low or high approaches for instance, ignoring the approach merely transposes to a 3-5/4-5 point, 3-4 invasion jōseki: the approacher cannot force any extremely significant local advantage if the defender plays elsewhere once. In one line, responding to a standard 3-4 corner approach is big but not necessarily urgent. This ultimately ties back to direction of play: if the direction of play is elsewhere and sufficiently important, it is acceptable to tenuki once from a distant 3-4 corner approach.

To summarize:

Standard approaches to a 3-4 corner can be bad at controlling the direction of play.

This means that it is important for you to have options in your library that give you agency over the direction of play as the approacher to a 3-4 point; we saw how crucial this can be for the 4-4 point in our article on the 4-4, 3-4 invasion. For all the strengths we discussed in our recent article on the attach-draw back jōseki, you cannot play high-level baduk if this is your only option on the approach. Therefore in this article, we will begin developing some options for the approaching side to dictate the direction of play against a 3-4 point, with a particular focus on the 4-4 attachment.

Three methods of choosing a direction

In the above diagram, we begin with a Black 3-4 stone and assume that White wants its stones to be directed toward the bottom side. White has three typical ways to play locally in a way that may allow for this to happen.

The first option is approaching from the bottom side directly, e.g. A. This is a situational move that was most popular against Chinese-style fuseki, but such fuseki largely disappeared from top professional play in the post-AlphaGo era, taking this approach with them. From a purely local perspective it is a loss for White: allowing the corner enclosure is very large and the approaching stone is unlikely to get equal compensation on the side even with another move. It should be viewed as part of a special strategy rather than as a standard approach: White prioritizes the bottom side so heavily as to allow Black a pretty big corner enclosure in exchange.

The second option is B, the high approach into the avalanche. AI’s most likely local response to a 3-4 one-space high approach is to attach below, as this is the most that best secures a decently sized corner against the high approach. Instead of going into the attach-draw back jōseki, White instead plays the 4-4 point and enters the (pre-)avalanche shape. This is one of the most common methods used by AI engines to alter the direction of play against a 3-4 point; however, it has two disadvantages. The first is that Black need not go along with White’s wishes and make this shape: Black could move out along the bottom side first, or even tenuki. The second is that this sequence can lead to the small avalanche, a notoriously complicated jōseki. Complicated jōseki are not only more challenging to learn, they tend to be very sensitive to the global board-state. Even if the avalanche gives you the correct direction of play, it is possible for you to get an unfavorable outcome based on several other factors on the board. Therefore it is a bit difficult to rely on the avalanche as a go-to method to change the direction of play.

The 4-4 attachment is a good middle ground. Unlike an approach from the side, the 4-4 attachment does contest the corner and prevents the defender from getting a major local advantage. Compared to the high approach, the 4-4 attachment discourages tenuki and has a better shot at giving you a position in the direction of your choice: moreover, the lines are generally fairly simple. We will see that not only is the 4-4 attachment a situationally viable way to approach a 3-4 point, there are times when it far outshines any other standard approach.

The 4-4 attachment

We can summarize the idea of the 4-4 attachment as follows:

1. The 4-4 attachment offers the defender a choice: take a locally favorable position at the cost of the direction of play, or give up the locally optimal outcome to contest the direction of play.
2. Compared to the low or high approaches, the 4-4 attachment demands an immediate response.
3. As the first corner approach of the game, KataGo rates it as about a 0.4 point loss - it is not good to play it willy-nilly, and the loss must be made up by direction of play.

There are three main lines to the 4-4 attachment: the hane (A), inside extension (B), and outside extension (C). Before we describe each line in detail, let’s get a basic understanding of their implications.

The basic idea of the 4-4 attachment is to offer the defender a choice between the hane and the other two options. The decision breaks down along the following lines of thought:

1. From a purely local perspective, A is the best option. It is the response that keeps the largest corner and in fact the outcome is locally favorable for the defender. However, it also introduces a symmetry into the position and thus gives control of the direction of play to the approacher.

2. B and C let Black continue to contest the direction of play. However, in return Black does not get as large of a corner - from a purely local perspective A is preferable.

Main lines

Hane

The hane is the main line to understand. It creates a local symmetry in the position which hands over the choice of direction to the approacher (White in this case). White will hane in whichever direction corresponds to the direction of play.

A few different continuations are possible by Black, but there isn’t any pressing need to learn all of the continuations in the diagram. If you want to keep things simple, then this is all you need to remember:

1. Atari after the hane (move 3, A). White connects and Black connects the corner. White can tenuki from here or push a few times.

2. Do not try to cut White. Black has two weaknesses to cover after the cut but can only cover one.

The result after A is slightly favorable to Black. We can see this via tewari analysis, comparing to the 3-4 low approach kick jōseki. White has made an unnecessary exchange that removes some of the aji in Black’s corner and filled in one of White’s liberties. This is certainly a significant advantage, but not game-breakingly large. In compensation, White gets to settle in the direction of its choice. Before entering the hane line, Black needs to judge carefully whether this exchange is worth giving White the correct direction of play; of course, the decision will depend on the surroundings heavily.

Inside & outside extension

If Black does not want to totally cede control of the direction of play, then its main options are to extend either toward the corner or the outside. Extending toward the corner transposes to a 3-3, 4-4 approach jōseki, which can then proceed in many ways; we show only a few lines to illustrate the possibilities. Extending toward the outside generally gives White a group facing the right side, away from its desired direction of play. However, in return Black cannot get as large a corner as in the attach-draw back jōseki or the hane variation discussed above. White does not necessarily need to finish the sequence in either case: simply forcing one of these two responses already limits the size of Black’s corner and gives White a useful outside stone.

Simulated example

Using KataGo, we simulate a scenario in which the 4-4 attachment is a viable approach option to the 3-4 point, and show how play continues.

Here the point of concern is the incomplete double low approach jōseki that has been played in the top left corner. White and Black each have a weak group here, White on the basis of having at best one eye and a weakness at E16, and Black by virtue of having a single stone close to stronger White stones. Therefore the direction of play here is clearly the top left. As such, it is possible to play the top left directly, and indeed KataGo rates moves such as B15 as among the best options.

However, there is also an open 3-4 corner in the bottom left, and in the context of this article we ask: what happens if we approach first? KataGo’s response is quite clear-cut: both the low and high approaches are significant mistakes, losing anywhere from 0.8 to 1.0 score. However, the 4-4 attachment is considered right up there with B15 as another essentially optimal continuation.

In this particular case, the top left is so urgent that KataGo is willing to tenuki in response to the low and high approaches: after all, even if Black plays twice in the bottom left, at worst this only transposes to a 5-3/5-4 point, 3-4 invasion jōseki. In fact, against the low approach KataGo is even willing to tenuki three times from the bottom left corner: spending four moves to capture the corner is not worth it for Black at this early stage, especially given that White still has some aji remaining there.

The 4-4 attachment invites White to take the locally favorable trade in the bottom left, in exchange for Black gaining some extra strength on the left side. Normally in the 4-4 low double approach, the outcome is acceptable to good for Black if Black can settle both sides cleanly. Meanwhile, since White starts on the back foot (having one fewer stone locally), White wants to settle as cleanly as possible and usually does so by attacking whichever of Black’s two groups is weaker. By gaining some strength in the bottom left, Black discourages any severe attack (such as a pincer) by White against its stones in the top left. Instead White is forced to stabilize its group by pressing from above, which lets Black settle cleanly while taking a little territory to boot. As a result, Black essentially uses its locally unfavorable outcome in the bottom left as payment for a locally favorable result in the top left.

Not all examples are so clear-cut as this one, as in this example the top left was particularly urgent. In more typical scenarios, the difference between the 4-4 attachment and either the low or high approach is often very slight, on the order of 0.1 score. As a rule of thumb, the 4-4 attachment as the first corner approach is a loss of about 0.4 score, but if there is a weak group in the corresponding direction then it is often enough to bring it to at least even with the low or high approach.

Conclusion

As we have seen from the example, the standard approaches to the 3-4 point are not always viable options due to their lack of immediate pressure and lack of ability to transition the direction of play. As always on this blog, we emphasize the importance of finding the correct direction of play, and having options to shift the direction of play when necessary. For that the 4-4 attachment is an essential tool, and is relatively easy to learn as well. The key to making good use of the 4-4 attachment is to get a feel for when direction of play considerations outweigh the local sacrifice intrinsic to this move.

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