Attachment invasion of mixed three space extension

Invasion  

Please elaborate.

Charles This is one of the (two) standard invasion^[3] points.

(DaveSigaty: I can't fully agree. This move needs to be put in context ^[2])

Charles Someone else referred to Attack and Defense - the book, re another variation for this shape - and that calls this a reduction. Well, maybe it is: and maybe it can turn into a kikashi sequence too. In other writing I have used 'invasion point' as a term for vital point in loose extensions.

Possible answers  

Any of a to d is a possible answer by Black: all we can be sure is that Black should react directly to .

Staircase  

The most common way is , and then White really must play for a staircase at . Now Black might connect solidly, or play atari allowing White to set up a ladder. White ought to check the ladder before playing the attachment.

Staircase: connection  

If , it is expected^[1] that White plays to try for a sabaki result here: White could indeed connect at p, too, but that may be too heavy in practical play.

Staircase: ladder  

If atari then, given a good ladder, White should be happy up to . Otherwise White should play as kikashi and look to create a good ladder by fighting.

Staircase: descent  

The low play here has been played by some very strong players, recently. It looks submissive, and White may not feel inclined to continue here.

It was played in a title match O Rissei-Yoda Norimoto (B)1996-04-04 (colours reversed) Later White played down with a as a kind of inducing move: after Black b, White c, Black d White had stones in the centre and a serious cut at x to target.

Side formation 1  

Here is the typical move. Other frequent plays are a and b. The attachment at c is not common.

Side formation 2  

When the stone on the left is high, the critical area is still on the right. remains by far the most common play. Now however, the idea of pressing down with b or c is more common than the invasion at d. The attachment at e remains rare.

Yi Chu-yong (W) - Cho Hun-hyeon, 26th Wangwi League?, 1991-07-26

 

The invasion starting with is seen when Black's position after will be overconcentrated. This is one typical case.

 

The game continued like this. Notice that Black has played a total of 8 stones in the lower left side, capturing just 3 White stones.

Yi Ch'ang-ho (W) - Cho Hun-hyeon, 35th P'aewang, 2001-01-12

 

In this example Black responds aggressively with the cut at . Play continues naturally until which attempts to break the ladder on the lower side...

 

recaptures the ko

When White responds with the right side transposes into the second example of the attachment invasion in this game. With White repeats the cut that Black played on the lower side.

[3] Keshi, no?