Invading At San-San

British Go Journal No. 41. May 1978. Page 20.

Part 1 of this series is on page 20 of BGJ 40.
Concluding our introduction to the basic principles of invading behind a hoshi stone, the 4-4 point.

Diagram 0 BGJ had this diagram and that for Page 21 swapped.

We concluded last issues article with this position and the statement that white is dead unless he has a stone further to the right which will enable him to take advantage of the cut above black 6.

In fact, although this diagram is very bad for White and he would never play like this except in the most unusual circumstances, he can live in an abject and groveling manner. Dia 1 shows how.

Diagram 1

White 1 is tesuji and black 2 is best. White connects underneath and black jumps ahead of him with 4, calmly pressing white along the second line. After black 12, white is alive with one eye in the corner and one eye on the edge, but black can play one point below 12 and force an answer and his influence towards the centre is superb.

Diagram 2 [BGJ had dia rotated 90°.]

Dia 2 shows whites correct play. Black 6 forces white 7 or white will die unconditionally. The result is ko, because of course black 8 will take white 3.

The point of the ko is this: if White wins the ko, he will live in the corner, but even if he loses the ko he will get two successive moves elsewhere.

Of course, Black gets two successive moves elsewhere if White wins, but the decision to invade the corner in the first place was Whites, so you can assume that White has taken this into account.

Note that if Black wins the ko, he will have played five moves in the corner to Whites four. So isnt the result just the same as Black playing one move to defend the corner? Yes it is, except that, again, it was Whites decision to start the ko. So the question boils down to this; if White has made a threatening move elsewhere instead of white 1, would Black have ignored it and made a protecting move, say at 3?

Diagram 3 [BGJ had dia rotated 270°.]

When Black has made a one point jump from hoshi, the commonest amateur sequence is that in Dia 3. White 11 could be played one point to the right. White is easily alive, in fact too easily; by naively pushing at 3 he has made Black unnecessarily strong on the outside. Black has no weaknesses to speak of and can now play elsewhere.

Diagram 4 [BGJ had dia mirrored.]

A more cunning move is white 3 in Dia 4. After white 7, white can either capture 4, or jump to A. Positions like this in which black still has some weaknesses are vastly preferable to the settled uninteresting sequence of Dia 3.

Black 4 is given in the diagram because it is the commonest and simplest move, but it is not the professional move, which is to jump to A instead. White then lives in the corner, getting a group which is very similar to that achieved by capturing 4 in this diagram. But there is a subtle possibility left that if black gets a move somewhere above A he can spring on white a sequence that kills him. Black should also think of leaving white with weaknesses!

This sequence may be found in standard joseki books. Desperate pleas from readers for enlightenment may be heeded in the next issue!