Large avalanche - turn inward

The inward turn: the threat  

This is an invention of Go Seigen, and was first played in a game against Takagawa in the League of the 'Strongest Player' (Saikyo) tournament in 1957.

Its main idea is that if White answers with here, Black next turns at , and after some standard variation of the outward turn has been played, the exchange of for will have given Black two free points compared to playing at directly. Of course, for a professional player to lose two points without any compensation is unthinkable, so this in general is not played.

The start of the joseki  

To avoid the variations as mentioned above, White exchanges for before playing at . The moves to invariably follow.

A mistake  

is joseki, but this is a mistake. , making miai of and , brings White to an uncomfortable position. With correct play, White will manage to save her three stones and live, but while White is only making two eyes, Black will get superb influence.

The main line completes  

Although there have been attempts with different moves, the sequence from to here is by far the most common.

Main variation  

The main variation of the sequence above is the one where is played at the top as shown here (sometimes is played at already, followed by and ).

White accepts that there is a chance of losing her three stones at the left, and takes influence at the top instead. Black next can choose among a, b and c and others; I will give one possible continuation for each.

Main variation a: the vital point  

is forced, after which is one possibility. proposes an exchange (see the next diagram) with each player capturing some stones, but Black refuses, and fighting will continue on the left side. Black has some very bad aji in the corner though, White being able to set up an approach ko here with White a.

Main variation a continued (31-32-33 at a-b-c)  

Black squeezes with and further to build thickness.

Main variation b: Black extends on the side  

is the most common variation, after which the variation to is forced. and form the most common continuation. After this, the fighting is not over, but there are no more standard variations.

Main variation c: Black extends  

is usually played at , which leads to the situation above with a different move order. ^[1]

After the cut with , Black captures two stones. Black has taken about 20 points of profit in the corner; White will have to make up for that through her advantage in the center fight.

Another Black variation  

For Black, another variation that has been tried is this instead of in the final diagram of the main line.

is the key move here. It creates the approach ko (also mentioned above) of White a, which makes this variation problematic for Black.

After the main line  

After the main line, Black can play a, allowing White to extend along the left side, or Black b, preparing to play on the left side himself, or he can play tenuki, probably making preparations to sacrifice his three stones.

In the corner, the three stones have been captured, but there is still some important aji left.

Double ko  

If White plays and , Black should not play immediately, because in that case White will play . This creates an approach ko, which in this position is a very good result for White. Instead, Black should exchange for first, then play .

Now White is captured because of double ko. However, this also means that White has an unlimited source of ko threats here, so she will win any ko worth less than about 30 points anywhere on the board.

A sente move  

After , she again threatens an approach ko, but Black can avoid it again, this time by playing at . However, after these moves, is almost sente, because a follow-up at a threatens to connect underneath.

Having the possibility to play in sente gives White an advantage in any fighting that might break out at the top.

The most common continuation  

is the most common continuation for Black. White usually answers by making a base for her left-side group with . The moves to may be considered the standard continuation of the joseki. Instead of , White a-Black b is also possible.

For the variation where White plays at c, I refer to Ishida.

A special strategy  

denotes some special strategy. is a natural answer: White plays the point that Black neglected to play.

Game example  

The reinforcement of was necessary because the aji of Black a was too menacing. Played between Rin (Black) and Ishida for the 1971 Honinbo title.

An aggressive move  

is a more aggressive move. Black intends to build up strength here, then make a checking extension on the left side. The tough answer at is the most common answer, but white also sometimes plays a, or plays her sente in the corner, starting with b, first. Black builds a wall with to , then attacks with . If he does not want to make White so strong this way, Black might also play at instead of or .

Continuation  

White attaches at and pulls back.

After , White can attack with moves like a or b, and both players will go on towards the centre.

-- AndreEngels

Black extends  

Someone commented that the joseki then continues:

Ladder  

White wins in the corner, but according to the commentator it all depends on a ladder at . I do not yet see it.

Ladder  

fractic:
Kogo's joseki dictionary gives this line. looks very ambitious.

Ladder  

fractic:
If Black does not have the ladder he now has to play a. He'll get the three white stones but White captures Black's lump with b.

If Black does have the ladder he can connect at c and, since the ladder starting with b no longer works, White is devastated.

Patrick Traill:
I am not sure I understand:

If by “the ladder” Black may or may not “have” you mean the ladder starting with White b, then the conclusions seem right — but I am confused to read that it “no longer works” after c, if you assumed it did not work anyway. Also, if that ladder does work, c does not stop it working.

If you do not mean that ladder, I cannot see which you do mean.