Standard opening 1
The following is a standard opening. It has been thoroughly investigated by Cho Hun Hyun and Lee Chang Ho. As a result of their experiments, it was modified substantially and often occurs in Korean pro games of the '90s. We start with four corner star points.
This joseki can not be separated from whole-board opening strategy, just like many other contemporary josekis. This means, showing the sequences of this joseki with local diagrams doesn't make sense.
was cho 9p's new move which was different from the traditional one. In old version, instead of
, defending b's weakness with
right after
had been the common sequence.
is a move which tries to make use of black's 2 hoshi formation on the right side. In this respect, it displays whole board thinking.
Now White faces the decision where to move next. is considered whole board joseki[1] after which Black patches up the weakness at a.
is considered mandatory, because a black move there would be sente for the threat at a). Black continues utilizing his thickness to play on the left and apply pressure on White's corner.
is a standard diagonal haengma to prevent being enclosed by a double keima. (Dieter ignores the exact reason for
).
When black approaches White's upper left corner with , white can not ignore it and instead capture the black stone on the left side [2]. Thus,
-
is a very natural flow of stones, nearly a necessary order of moves.
At , the standard opening comes to an end, that is to say, professional players believe that no further research is paying off and this has found its way into standard (Korean) textbooks.
[1]
This gives quite a bit of cash? at the bottom left. However, after
, Black takes a global lead, or rather, the position is considered active? for Black. So,
is called a whole board joseki mistake.
tapir: The amount of cash is limited by the availability of the 3-3 invasion for black.
[2]
White would like to resist Black's speedy play by punishing him for leaving the marked stone unattended, but Black sacrifices the stone and takes sente to play in the next diagram. This is again called active for Black. Hence
is a whole board joseki mistake.