BQM 173

Does the san-san invasion work?  

Bill: What do you mean by work?

Main line  

I'd call this the main line continuation. Now what?

Passive answer  

If and , is required to save the corner territory. White has profited a little, but it really depends on how seriously the open skirt at a should be taken.

Active answer  

If this way, the life-and-death in the corner turns out to be a little tricky. is the typical shape to live here. It seems that White is just alive; Black could cut next at the circled point, but would have to be concerned about being shut in.

There are other variations. On balance it looks like the invasion would very often be quite a useful move.