Shoulder invasion of mixed three space extension
One of the three-space extension invasions is a shoulder hit on the lower stone of a mixed-height extension.
The shoulder move
is one of the more common moves against a mixed three space extension, Black a, b or tenuki is to be expected.
In practice it is played as ladder breaker, actual or preemptive, as reduction, as focal play in the context of larger frameworks, as a forcing exchange to strengthen a weak group on the outside, or in a fashion similar to a leaning attack.
If intended as a reduction White moves at c or d, which are commonly answered at e and f, respectively, are more often seen than the shoulder hit.
Some possible sequences
![[Diagram]](../../diagrams/9/920e734a5ce024474d14cead1299115e.png)
Similar to a shoulder hit on an unsupported stone
Slarty: on an open board, Black can probably be pleased to answer
at
. It's then not possible to separate the black stones without acquiring a heavy shape. Not sure if there is a SL page for normal shoulder hit side josekis.
tapir: Well. This is practically never played on open boards, hence midgame. If separating is the main intention I wouldn't start with
, which offers Black options to connect. In this variation if Black does not connect, White has an option to separate, that does not need belittling. White at a later does not look like bad shape to me. (Transposition of a midgame joseki when Black invades White, afaik.) Finally, SL coverage of midgame joseki is pretty bad. Reduction techniques was a good start for reductions, but the individual pages are lacking content.
Slarty: It's true if
somehow gets Black to play elsewhere, W has an option to cut. Probably the point to the left of a. If a, B can respond at the point to the right of a.
When Black can't afford being cut off from a weak group in the center
might be necessary, which allows White to break in after e.g.
at a.
![[Diagram]](../../diagrams/29/972b304b85b6356fec4a1b5fa0e19fd3.png)
![[Diagram]](../../diagrams/9/771bdadf9b015d861148d83798af7458.png)
![[Diagram]](../../diagrams/52/d7fcf751d34959e63d79b723e517f1db.png)
![[Diagram]](../../diagrams/30/3d02ab3fd09d6843fabbc5beaa103a3f.png)
![[Diagram]](../../diagrams/18/e76d2630667dd4765e78542156d8430d.png)
![[Diagram]](../../diagrams/10/e8f0973bece6bef0cf236e277edd7f20.png)
![[Diagram]](../../diagrams/15/0762f9e7a467c94f1f4d0bef0f48cd8a.png)
![[Diagram]](../../diagrams/49/a31feabafe50dae4dca26a37958cc910.png)
![[Diagram]](../../diagrams/1/b318ffcf14dc52c2ad892a4720df958a.png)
![[Diagram]](../../diagrams/39/de8dc78d6069c77218a9be786a09758c.png)
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