In his work The Art of War, ...

By Rob Van Zeijst

In his work The Art of War, Gen. Sun Tzu suggests war and peace are indistinguishable parts of the same ongoing conflict. His theory codifies how a campaign is fought both at a military level as well as through diplomatic, psychological and economic means. Today his theories still find application on a wide scale. You can actually use Sun Tzu's insights on a personal level in go by using the "soft power of persuasion" to make your opponent see your point of view. That way you can subdue your opponent without fighting. Let us see how we can apply this idea on the go board.

Extensions

As we have discussed before, you should base the width of an extension on how strong your surrounding stones are. However, you must always take into consideration the stones of your opponent.

Diagram 1: In relation to his position at the lower right, black 1 is a very wide extension. However, black 1 puts pressure on White's position at the top. Because of the marked black stone, White's position has no base and is weak. Because of this, Black's extension at 1 is strong even if it looks overextended.

Diagram 2: In response to 1, Black hopes White will play at 2, which would be followed by black 3, white 4, black 5, or a similar sequence. This way, Black builds up influence while chasing White's group and may even be able to omit reinforcing his stones around A.

Diagram 3: However, in most games you will not have that luxury. In this game between two top Chinese pros, White first makes a two-space extension with 8 and 10. While attacking it, Black builds influence at the top with the sequence up to 19. White really wants to invade at 22 right away, but if he does so, Black may get sente (take the initiative) and switch to the lower side first. Black would probably like to play at 20 to make a maximum extension. Therefore, White plays at 20 to entice Black to extend to 21. White 20 can be called a 100 percent move while black 21 is only around 95 percent. At the same time, Black holds back slightly to keep the option of making an extension to A, while enticing a white (two-space) extension to B. However, at this point, neither of these moves represents the best value on the board. Next, White switches to the top with 22. Like the move at 20, White is trying to make Black play a subpar move. Black tried the same game with 21. A white extension to B is slightly inefficient, especially because the stone at 20 would then be better located at C.

Reference 1: From Black's perspective, 1 and 3 are the ideal combination to expand the lower side. White would probably be forced to start an invasion on unfavorable terms in this area. By exchanging white 1 for black A in the actual game, White forestalled this in sente.

Conclusion

Using a "diplomatic" solution, White contained Black's expansion and avoided being drawn into a battle that was unfavorable for him.

Solution to Aug. 5 problem

Solution 1: In response to White's marked stone, Black extended to 1. True, this is not an ideal extension, but it prevents White from extending to this spot and prepares for an invasion at A while reinforcing his own stones. To avoid the result in Reference 2, White then forces the sequence 2 through 7 and extends to 8. Later, 23 and 25 form an interesting combination that prompts White to make a choice between reinforcing at 26 or 27. White chooses 26, so Black plays at 27 to destabilize White's corner. The plan is to attack and reinforce around B. In the end, Black won this game.

Reference 2: The reason why White plays the marked stone instead of extending to A is that this would give Black an easy extension to B. What is worse, if the sequence through 7 is played at some stage, the A for B exchange is very bad for White. In the actual game, instead of forcing 2 through 7, if White plays elsewhere, such as at C, Black would play at 1, enticing White to cut at 2, followed by the sequence through 7. White's marked stone is now in grave danger.

Problem

Problem 1: In the actual game, why did Black choose the one-space extension in this situation? What is wrong with this two-space extension?

Van Zeijst is a four-time European go champion and European representative at the Fujitsu World Championship.