17

The 2 space extension is generally regarded as very hard to cut and thus solid, providing at least 1 eye with various options to gain a lot more eyespace easily. However, invasions and attacks are still possible. The B1 move in your diagram is actually a standard invasion with the marked black stone around. $$cm1 A possible invasion of two-space extension $...


7

There's an excellent and detailed answer already, but I want to throw in some other thoughts. I attended a workshop with Guo Juan (5P) where someone asked about the wall+1 rule and she explained that it's a nice mnemonic that works in some common situations (2-space jump between single stones, 3-space jump from 2 stones), but isn't much of a good rule past ...


4

Although it can and often does provide territory, that is not the primary reason that you want to play the two-space extension on the third line; what you're looking for with this extension is a base which is very difficult to cut, one which you can use to fight and/or secure territory as the game progresses. Unless black has support, white can easily ...


2

Question 1: Ignoring the three marked stones, how would one usually defend this invasion? Is J17 correct here? They really can't be ignored for a question like this. "This" invasion doesn't come out of nowhere (except vs. a belligerent beginner). Question 2: Is white 2 above already a horrible mistake? Or does there exist a follow-up after black 3 that ...


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