British Go Journal No. 8.  Spring 1969. Page 10.
Kaku Takagawa, 9p
An extensions main aim, we have found out, can be to avoid the sandwiching in process. It would only be logical that we have some means of checking the opponents expansion. This check is an approach from our lines.
Diagram 9 |
A check is a rather delicate thing to determine. For instance, in Dia 9, black 1 is a check, white 1 is not. To an expert these differ in meaning as the examples below will make clearer.
Diagram 10 |
In Dia 10, 1 prevents Whites extension to A or B and at the same time is an expansion; but it is not a check.
Diagram 11 |
In Dia 11, 1 is a check which does not constitute an attack against whites extension, but will facilitate an invasion at C. It is also an extension from the right corner, and prevents an attack on this corner from D.
Diagram 12 |
1 in Dia 12 also facilitates an invasion and serves as an extension but is not a check.
Diagram 13 |
But in Dia 13, the check of 1 makes a great difference. Now Black cannot approach the large extension from D. Thus we begin to notice that one of the effects of a check is to consolidate a large extension, with a very great effect.
Diagram 14 |
Move 1 made by black and white on either side of Dia 14 may at first sight look similar, but they are quite different in effect, because of the difference in the way the corners are defended. On the top blacks defence may not be shaken by whites move, but on the bottom side whites defence is shaken.
(It should be observed, however, that the corner defences have different purposes, so that whites weakness does not invalidate his position.)
On both sides the check move has been made from a maximum extension; the check should not in either case be cut down to a smaller span.
White can continue on top with A or B. This possibility would, of course, press on blacks lines, and, at the same time, allow white to expand.
These cases occur quite often in actual play.
Diagram 15 |
Before the opponent establishes or solidifies his lines, a wedge can be placed in between the left and right bases of a formation such as Dia 15. Once the formation is established a stone placed inside will be an invasion stone and not a wedge.
A wedge move is mostly played on the third line, where bases are usually established. These stones are usually placed below the side stars or on adjacent points, the idea being that, if an opponent approaches the wedge from one side, another stone can be placed as an extension on the other side. This is, of course, the ideal point of placement of a wedge; if there is no room for this type of extension then it becomes an invasion rather than a wedge.
In Dia 15 we have a wedge 1. Black must decide which way to attack
this wedge by considering the effects on the corners and the potential
spheres of influence for both sides. In this example black makes a good
solid base at the right but 3 threatens the corner. This does not mean
that 2 was bad, since after 3 the formation to the right compensates for
the attack by white on the left.*
* [BGJ had left and right swapped.]
[BGJ had Dia 16 at the top of the board.] .
Dia 16 shows the other possibility after 1; this is not very different from the previous example.
Diagram 17 |
[BGJ had Dia 17 at the top of the board.] .
In Dia 17, white 1 is placed one point to the right. Black plays to stop and 3 is natural. Black is satisfied with whites confined shape. 3 can be extended one further point (see Dia 24) but even so Black is under no disadvantage.
Diagram 18 |
If White plays his wedge from the other side, as in Dia 18, 2 is necessary. It is always played on the side containing the larger area, and cannot be played on the narrow side. In comparison with Dia 16 whites confined formation should be noted.
Diagram 19 |
Blacks defence against the wedge in Dia 19 causes White to extend to the left.
Diagram 20 |
[BGJ had Dia 20 at the bottom of the board.]
But in Dia 20 Black defends from the other side, where he has a small tight corner. This is a mistake, for 3 weakens the right corner. 2 would have been more effective if the left corner had been facing in the other direction (at ). In this situation, however, whites wedge would have been at A. Then if black defends the right, white extends to B and destroys the security of this larger corner. This causes Black to play C.
Diagram 21 |
In Dia 21, the wedge stone is placed in a symmetrical position. Thus the stones which are not yet shown on the sides must be taken into account before reaching a decision, for 2 and 3 could be reversed. Since the approach that black makes is quite important, he may delay his move in favour of another elsewhere. Then, from the situation that develops, he will make his choice; this is rather advanced tactics. A mere stone at A or B can upset the balance in favour of a particular way to stop white.
Diagram 22 |
Diagram 23 |
[BGJ had Dia 23 at the bottom of the board.]
Given the wedge play in Dia 22, which side should Black stop from? Furthermore, is 1 the best point for the wedge? What about 1 of Dia 23 instead? These are quite difficult questions to answer.
In Dia 22, 1 cannot be a bad move, as white can extend in either direction in answer to a check from right or left.
If we look at Dia 23, we see that black is still menaced by 1, for the sequence white 5, black 6, white 7 deprives him of his base. Thus 2 is questionable. He could have played against white at A, White answering B. This would prevent the aforementioned threat, but the exchange is not desirable for black. Therefore black must prepare a counter-move against white that will be more effective. Dias 24 and 25 illustrate this point.
In Dia 24 the choice where to place the wedge is a difficult problem. White could play A instead, but this is too narrow an extension. Yet if he holds to the 3 as shown there is an established line to use which makes black firm and white shaky: black 4 to black 8.
Diagram 25 |
[BGJ had Dia 25 at the bottom of the board.]
An alternative to consider then is Dia 25, with the wedge at 1. This is not quite satisfactory, for, after Black protects at a, he threatens a counter-attack on the weak white lines. White will then suffer from a greater vulnerability. Thus we finally see that the black response to the wedge from the right is better than from the left . If a wedge move is exposed to such a danger, then it could not have been a good move in the first place. The idea of placing such a move is certainly not to expose the resulting formation to extreme danger. Therefore even a very simple-looking wedge move requires careful consideration.
A wedge move is sometimes regarded as part of the tactics of the middle game, yet the wedge is mainly on the third line near the star, just as in the large placements (see issue 7, page 4). At this point there are a few additional points I would like to make about these large placements.
Diagram 26 |
[BGJ had Dia 26 mirrored left/right.]
In Dia 26 we see a large placement that can be easily overlooked. This check by black stabilises his position and, at the same time, makes white insecure. If white should occupy this important point, the stability would be reversed.
Diagram 27 |
In Dia 27, 1 strengthens black while building up threats against white. Here black will later be able to jump in at A. Again there will be a tremendous difference if white occupies this first.
Diagram 28 |
In Dia 28, we see another case where a one-point jump can be quite important to either side. On the upper side, 1 threatens whites weak corner. On the other hand, if White plays at 1, he protects the corner and also weakens black. Such differences due to occupying an important point first should be studied as they will improve your game.
Diagram 29 |
[BGJ had Dia 29 at the bottom of the board.]
Dia 29 shows a situation where White has played on the side but
has not make the consolidating move at 1.
[The BGJ sentence made little sense. Rephrased.]
Diagram 30 |
Black immediately threatens the action in Dias 30 and 31. White escapes death in Dia 30, but black has begun to build up a large area to the left. If white tries 4' at 6, then black 8, white 10, black 4 produces a formation of central power for black.
Diagram 31 |
[BGJ had Dia 31 at the bottom of the board.]
Finally, Dia 31 shows another variation for black which attacks the base of the formation and drives the white group towards the centre. This attack also gains black greatly.
Continued in part 3 on BGJ 9 page 8 .