I have been looking at §28 of 38 Basic Joseki, which deals with a double keima kakari against a stone on hoshi. I realise that this book is old and restricts itself somewhat, but I am taking it as a way of getting a grounding in joseki.
Most of the variants treated start with tsuke-nobi to pressure a squeezed stone:
$$B $$ --------------------- $$ - . . . . . . . . . . $$ - . . . . . . . . . . $$ - . . a x . W . . . . $$ - . . b X . . . . . X $$ - . . d w e . . . . . $$ - . . O 1 3 z . . . . $$ - . . v 2 c y . . . . $$ - . . . . . . . . . .
Other variants are given, with reasons for choosing them, but I cannot formulate a strategic reason for Black to choose tsuke-nobi because White can choose so many different responses to it with different results. Of course Black could play it from habit or just hoping for a certain response, but that seems less satisfactory.
The variants considered
- Tsuke-nobi: 1-3 as shown.
- W4@a —
- B5@x — White: side + corner; Black: large top, can swallow marked stone, sente.
- B5@d — White: corner + small top, sente; Black: side high and strong.
- W4@b — White: side, option on corner; Black: big top, sente.
- W4@c, B5@y —
- W6@z — Fight White: top weak, side medium, sente; Black: corner + cutting stones.
- W6@a — Tricky White: side weak, small corner, sente; Black: strong but little territory.
- W4@d — White: weakish top + side, sente; Black: decent corner, connected to centre.
- W4@a —
- Tsuke-osae: 1-2 as shown, 3@d — Peaceful White: see variants; Black: decent corner.
- W probably connects at v — White: moderately strong on both edges, option to reduce corner; Black: connected to centre, sente.
- W tries to enclose B (W4@3) — White: weak wall, sente; Black: shut in.
- Kosumi to 5-5: B1@e, W2@a, B3@x — Simple White: decent side + corner; Black: strong top, sente.
- Kosumi to 3-3: If B has stones on both edges B1@a, W2@e, Black cuts — White: two weak groups, sente; Black: alive in corner.
Examining these variants, it is clear that Black can choose tsuke-osae, 5-5 or (given pincers against both kakaris) 3-3 to achieve the results in the last three options above. But what strategic purpose is served by tsuke-nobi, regardless of where White plays 4 (a/b/c/d)?
What I hope for from the answer
- It is along the lines of If you want do do X, play A, but if you want to do Y, play tsuke-nobi, i.e. states the strategic goal served, maybe even gives an algorithm for choice. Obviously that will leave me to make some judgement(s), but at least I will know which.
- It assumes that I restrict myself to the above variants, and presumes my opponent does too, unless that assumption entails a severe loss for me. This because I am trying to impose some sort of limit on how much I learn for an initial grounding in this (and other) joseki. Comments on other variants may also be interesting, but are of subordinate importance to me.