This article explains the difference between extending in tobi or keima when our opponent presses our group on the second line. To illustrate this topic, this article centres around a joseki that we often found in modern go. This joseki is a good example to explain this difference between those two moves. Have a nice reading!
Classical joseki - Presentation
Here is the joseki which is the base of our article: black made a tenuki (or played a 4-5 step pincer) and white pressed him on the side. The classical follow up is to play at A or B. In the past B was rarely played. However, it gain a lot of popularity nowdays.
We will presents the pros and cons of those two choices, to know when to choose one over the other. We will then look at some examples from professional games.
Classical joseki - Tobi at A
First, let's look at the joseki when black plays A. Locally, white follow ups are: pressing at C, play in the corner at D or on the side at E.
We won't look at the C press as it is also possible for white to press when black plays keima instead of tobi at A. We will only have a look at the D move here and the E move will be seen in one of the example at the end of the article. If you want to explore all the possibilities, please have a look at the Josekipedia website : http://www.josekipedia.com/#path:qepcod.
Follow up at D
Move D aims at the cut in the black tobi shape. Different continuations are possible, the most usual one requires a shicho favourable for white. We will present here only this sequence and the final result.
The interest of this sequence for white is that it changes the direction of play: indeed, black had potential on the right side with his stone in tobi but after this sequence, it is white who by cutting this same stone occupies the right side and can create potential there. So depending on the overall situation, this result may be more interesting for white.
L’intérêt pour blanc de cette séquence est qu’il change la direction de jeu : en effet, noir avait du potentiel sur le bord droit avec sa pierre en tobi mais après cette séquence, c’est blanc qui en coupant cette même pierre occupe le bord droit et peut y créer du potentiel. Ainsi selon la situation global, ce résultat peut être plus intéressant pour blanc.
We see here that the black tobi in A leaves some weaknesses which white can aim at, if needed to change the direction of the game. If black deos not want to give this opportunity to white, he can play the keima at B.
Note that if black wants to develop his position on the right edge after white's move 1, he can play more simply as in diagram 4 :
After move 4, black keeps his position on the edge at the expense of his corner. So this is a choice to be made based on the overall position. In addition, the nobi black 2 is usually the suite that black aims for when he plays move A. If white does not play 1 directly, black A is a big move that effectively develops the right edge.
Classical Joseki - keima at B
With the keima B, black's position is a line lower than with a tobi in A and has less development potential. On the other hand, there is almost no aji in black's corner: white can no longer change the direction of play as effectively as before. For these two reasons, the right edge no longer has development potential for both players.
Localy, white follows up by pressing at 1:
Follows this joseki:
The sequence is kind of forced, and move 9 is honte and protects the cup. The result is different from the joseki with the tobi in A presented earlier because although black retains his corner, the influence is less strong because black can play the sequence 1 to 3 in the following diagram.
Also, one major difference is that the right edge remains open with a black move on the marked location as end game move. White has not changed the direction of play here, but has solidified the one he already had with those three initial stones, i.e., from the potential to the top side.
Joseki classique or moderne: when to choose one over the other?
After the presentation of the two josekis and their local continuations, we see that the joseki modern is preferred when reducing the aji in the corner or the does not want white to be able to change the direction of play by taking the right side.
The modern joseki is preferred when one :
- does not want the white group to stabilize easily,
- wants to limit the number of possibilities for white,
- (really) wants to prevent white from creating a moyo on the right side,
- the right side has low value.
On the other hand, as we saw, the joseki modern gives a lower position to black than the joseki classical. Therefore, the joseki classic will be preferred when black wants to create territory on the right side. Thus, if a black stone is present in the lower right corner, it is advisable to play the joseki classic to develop the right side.
Here are four examples from professional games. In each of those examples, you can guess which move between A or B was chosen.
Problème 1 :
B is preferable. White's position in the northwest corner (marked stones) is solid and low, so the north slide has little value. Having a low position is not a problem for black. He plays B with the intention of reducing white's possibilities in the north-east corner.
Probleme 2 :
White plays B because he does not want to give any forcing moves to black on the north side. If white plays A, one possibility for black would have been to play according to the following diagram:
In this diagram white answers 2 in 3 so as not to be locked in. Black naturally builds points on the north side which is not very pleasant for white. White has played B to avoid such a continuation.
Problème 3 :
Black has potential on the north edge thanks to his marked stones: he plays A in the hope of developing this potential.
Problème 4 :
Avec son shimari dans le coin sud-ouest, blanc a du potentiel sur le bord sud. Noir joue B pour limiter ce potentiel blanc. Si noir avait jouer en A, blanc aurait pu viser une suite similaire à celle montrée dans le problème 2.
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