We will present Joachim Meinhardt's alternative move suggestions, which basically capture all of White's stones at the left side of the board, but leave Black's upper left corner vulnerable to attack, due to the unfinished Crosscut Sequence in the left centre.

We will also address a topic here that should comfort many amateurs: Even professional tsume-go specialists do not always succeed in having all the specific mechanisms of the problem consistently at hand.

KataGo - as usual - has some sharper moves on offer, but in principle fully confirms the validity of Joachim's considerations for handling the semeai in the upper left corner, which, despite all their efforts, ultimately end in Black's defeat.

Let's go back in time and enter the world of amateurs ...

: ( 2022MainLine)
Joachim Meinhardt investigated very intensively the question of whether Black could successfully capture White's group on the left side with , instead of terminating the Crosscut Sequence in the upper left centre with a move at .

Please note that White's group in the upper right must seek independent life, as capturing the hanezeki's tail with in the case of emergency will not lead to success overall.

Please also note that the forthcoming fight for life and death may not be limited to the upper left corner, but could spread to the upper side of the board and eventually result in a semeai between White's centre group and Black's large group in the upper right.
This case would be hopeless for Black from the outset if he had already played the Guzumi Exchange , .

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White's push into Black's upper left corner is the only move.

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Black's connection is forced.
As a matter of course, Black has to prevent his single stone in atari from becoming captured.

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White's second push into Black's corner is decisive, largely weakening Black's formation, as we will see below.

: (A 2035)
Retreating with the jump to is the strongest move for Black here, providing maximum resistance.

As you will see further below ( 2035), KataGo's favoured sequence basically follows Joachim's elaboration (which is why this is not shown again in detail here).

Black might consider blocking at , instead, but which will not benefit him either.
In his 2010 book, Cheng favoured this alternative move, which we will present in detail next.

So let's take a detour to China first ...

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Cheng also covered this move in his 2010 book on Igo Hatsuyōron (but not in his original 1988 one) - i.e. without my Guzumi and Harry's Hasami-Tsuke, but with my Second Kikashi in the hanezeki.

However, we found that his corresponding sequences were erroneous, which is understandable considering that solutions to 203 other problems still had to be addressed for the new edition of his 1988 book.

Further details of our analysis at that time can be found at ...
363
... and ...
532

, , :
The first three moves in the upper right corner are mandatory, as already explained above.

: (A 2035) ( 2035)
Cheng considered this solid turning move as the best choice for Black.

Cheng also showed a few variations after KataGo's favourite in his 2010 book.

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As a matter of course, White connects her single stone in the corner.

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Black's small knight's jump to is a desparate attempt to keep his forces connected.

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White pushes further into Black's corner, creating cutting points in Black's formation.

In each case, KataGo favours here, resulting in a change in the order of moves with the correct continuation.

: ( A 2035a)
White's throw-in in the corner aims at creating a shortage of liberties on Black's side.

Again, KataGo favours , resulting in a change in the order of moves with the correct continuation.

Playing the hane at the left edge first would also result in a change in the order of moves.

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Black connects.

Capturing White's just played stone with will not help either.

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White's hane at the left edge aims at , , , , .

For another time, KataGo favours , resulting in a change in the order of moves with the correct continuation.

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Black connects, preventing White's throw-in at the same point.

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Finally, White cuts at the top.

: ( A 2035b)
This move, resulting in White's success according to Cheng, is a mistake.

KataGo favours , instead, resulting in a ko-fight that Black will be unable to win.

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Black occupies a liberty of White's two stones.
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White gives atari in the corner.

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White's connection at the upper edge is tesuji.

: ( A 2035c)
Black's sagari to the upper edge, chosen by Cheng, is a mistake.

As Joachim discovered, Black must play at , instead, taking White's cut-off group a decisive liberty.

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White starts the reduction of the liberties of Black's group at the left edge, ...

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... while Black is busy with taking White's four stones at the upper ege off the board.

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Finally, White gives atari at Black's group at the left edge.

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Black connects at the top, securing life for his remaining stones there.

He is unable to connect at , instead, as White would continue with giving atari at , killing the entire corner.

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White captures seven Black stones, securing independent life for her group in the upper left.

Please note that Black cannot hope on a semeai between his large group in the upper right and White's centre group.

All of Black's groups in the centre and the right half of the board are dead, so this would be a great success for White.

Please note that White willnot capture the hanezeki's tail with a move at .

White will win the game by a large margin.

2035

And now let's find out what KataGo thinks about this matter ...

Referenced by ( 2035)

: ( 2035)
KataGo follows Joachim's suggestion by retreating with .

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KataGo will follow Joachim's ideas, of course with the AI typical changes in the order of moves.

White pushes into Black's formation at the top, aiming at creating cutting points.

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White's cut is decisive.

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Black's protection of this cutting point at is more forcefully than Cheng's suggestion of the solid connection with .

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White connects her single stone in the corner.

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White's kikashi at the left edge, forcing Black to conne t at , could also be played a bit later.

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White's series of atari forced Black to capture White's cutting stone with .

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White's descent to the upper edge threatens to reduce Black's corner group at the top to only one eye.

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Black secures independent life for his remaining stones in the upper left.

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White makes sure that she will win the semeai with Black's cut-off stones below.

Alternatively, she might consider immediately occupying a liberty of these stones with a move at .

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Black's throw-in creates a false eye for White's centre group.

White's group in the upper left is independently alive, so Black now sets his hopes on a semeai with White's centre group, aiming at forcing her to capture the hanezeki's tail with a move at .

This starts a variation of Joachim's Ko-Semeai, in principle.

For further details, please refer to section "Joachim's Hiki at the Upper Edge (Joachim's Ko-Semeai #1)" ( 2034)

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White is forced to capture.

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Black secures an eye for his large group in the upper right by capturing White's single stone in the right centre.

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White occupies the Guzumi Point, stopping Black from creating a second eye in this area.

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Black now attacks White's eye shape at the top.

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KataGo favours peeping with the diagonal move at , which it found so very late during its initial 2019 training session.

Joachim answered Black's previous push by immediately blocking at , and destroyed Black's shape at the top with a move at later.
The outcome of the ensuing semeai is not affected.

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KataGo inserts a kikashi for Black, ...

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... before playing the mandatory connection with .

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White secures her eye at the top.

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Black instends to create a ko-shape in the right centre.

Not playing to before (as Joachim used to do), creating another ko-shape at the right edge, does not make a difference.

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Black's descent to the upper edge prevents another ko-shape at the top, which would largely favour White.

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An "early" kikashi, typical for KataGo.

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White simply continues with occupying Black's outside liberties.

The outcome of the semeai in the right half of the board is yet decided.

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Sooner or later, Black will have to connect the hanezeki's tail and capture the entire left side. White, however, will capture all of Black's groups at the right, which is larger.

White will win the game by a large margin.

2035

2022MainLine