Michael Redmond 9p once discovered a Black follow-up move to Harry's Hasami-Tsuke Sequence in the upper right corner: his Kikashi in the Bamboo Joint.

In principle, this Kikashi presents White with the choice between profit or Main Semeai Liberties.

An unexpected interaction with KataGo's new moves on the left side of the board, however, now leads to KataGo evaluating this move as a two-point mistake.

In the "classical" environment of the problem (i.e. with White occupying the Guzumi Point), Michael Redmond's Kikashi retains its significance, for it continues to favour Black in it.

Within Harry's Hasami-Tsuke Sequence, however, KataGo has a White tesuji up its sleeve that makes it imperative to play Harry's Hasami-Tsuke "early" in the course of the "classical" solution sequence.

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

: ( 2022MainLine)
In 2013, Michael Redmond was extremely kind enough to give us his assessment of our findings so far.

He outlined some aspects that were previously escaped our attention, when evaluating the pros, and cons, of Harry's Hasami-Tsuke Sequence , in the upper right corner.

Michael Redmond suggested his Kikashi in the Bamboo Joint for settling the shape.

Please note that we utilised my Second Throw-in in the hanezeki at that time, but played the upper kikashi , later in the game.

Michael Redmond explained the atari and the solid connection to us as White's options for her response.

A - The atari:
The atari at will benefit White territorially, as she will be able to capture Black's pivotal hasami-tsuke stone .
The drawback is a loss of one tempo in the Main Semeai, as Black's large group in the upper right has an additional liberty at thereafter.

B - The solid connection:
If White cannot affort providing Black with an additional Main Semeai Liberty, she will choose the solid connection at .
The drawback is a territorial loss in the upper right corner, as White will be unable to capture Black's hasami-tsuke stone thereafter.

For further details of our analysis at the time, please refer to the history of our investigations ...
390
... and ...
838

Let's try to find out what KataGo thinks about this matter ...

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KataGo answers Michael Redmond's Kikashi with the atari at .

Please note that this move loses one tempo in the Main Semeai, so White must not give Black any opportunity for playing tenuki.

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It follows the Crosscut Sequence in the left centre.

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White plays the first move at the left side, as usual.

; :
KataGo likes to play the kikashi in the hanezeki "early".

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Black continues with the Nakade Sequence.

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KataGo waits until the last possible moment for initiating the Guzumi Exchange.

For further details, please refer to CHAPTER "Timing of the Guzumi (2022)" ( 1813).

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KataGo's Atari in the Nakade Area.

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Black follows KataGo's 2019 line of play here.

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Black ends in gote in the Nakade Area.

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White starts the reduction of Black's upper left corner with Yamada Shinji's Tsuke.

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KataGo's Immediate Crosscut.

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Now the moment has come when it becomes clear why the early exchange of for was a mistake: Black can only get one of the two moves and , but not both.

It is best for Black to connect his pivotal hasami-tsuke stone, which limits his loss to two points.

Blocking the upper left corner with would be one point worse overall.

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KataGo likes to capture the nakade early.

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White's hasami-tsuke starts the reduction of Black's lower left corner.

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KataGo moves to the top left corner as the continuation in the lower left is gote locally.

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White plays the final atari in the lower left corner.

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As usual, it is best for Black to tenuki to the unfinished position in the upper left.

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Black ends there in gote.

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KataGo's Bad-Shape Move in the left centre.

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Black plays KataGo's Solid Connection in the left centre.

Playing at in the right centre, instead, would not affect the outcome of the game, but lose one point in the Semeai Variation only.

Black plays 3/3 reductions.

Capture Variation:

Compared to Our Solution (2015 / 2017), ...

• White destroyed four points of Black's territory in the upper left corner.
• White got an additional point of territory at the upper edge.
• White destroyed one point of Black's territory in the left centre.
• Black destroyed one point of White's territory in the right centre.
• White's cumulated gain in the lower left is six points.
• White did not capture Black' stone in the lower right, so losing two points.

In total, Black lost nine points.

Black + 5 => White + 4

Semeai Variation:

Compared to Our Solution (2015 / 2017), ...

• White destroyed four points of Black's territory in the upper left corner.
• White got an additional point of territory at the upper edge.
• White destroyed one point of Black's territory in the left centre.
• Black captured one White stone more in the left centre, so gaining two points.
• Black destroyed one point of White's territory in the upper right corner.
• Black destroyed one point of White's territory in the right centre.
• White captured two Black stones more at the left, so gaining four points.
• Black's cumulated gain in the lower left is two points.

In total, Black lost four points.

Black + 3 => White + 1

Let's return to the world of amateurs, arriving a few years after Michael Redmond's kind advice ...

Referenced by ( 2024)

:
Joachim Meinhardt discovered that Michael Redmond's Kikashi in the bamboo joint has its special merits in the classical line of play, where Black chose Harry's Hasami-Tsuke Sequence , for reducing White's corner territory.

Please note that White occupied the Guzumi Point after the completition of the entire Nakade Sequence at the left side of the board.

Again, White has to make her choice between territorial profit (with the atari at ) or keeping Black par with the Punishment Semeai Liberty Level (with the solid connection at ).

For further details of our analysis at the time, please refer to the history of our investigations ...
1092i

Let's try to find out what KataGo thinks about this matter ...

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KataGo starts with occupying the Guzumi Point.

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KataGo likes to insert the last kikashi in the hanezeki immediately.

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Black's push starts the reduction of White's upper right corner.

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As a matter of course, KataGo continues with Harry's Hasami-Tsuke.

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However, KataGo prefers a different termination of the sequence, the solid connection with .

KataGo is very aware of the territorial disadvantage (of two points overall, as we will see below) that would result from Michael Redmond's Kikashi , should White play the "usual" move at .

This implies that Black should have played Harry's Hasami-Tsuke sequence much earlier in the game ( 2032).
Please remember that this is possible - contrary to Fujisawa Hideyuki's classical reduction sequence - as Black ends in sente, not in gote.

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Black must follow White with the Main Semeai.

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White starts the reduction of Black's upper left corner with Yamada Shinji's Tsuke.

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KataGo's Immediate Crosscut.

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KataGo likes to interrupt the sequence in the upper left corner for settling the shape in the upper right.

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White continues in the upper left corner.

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White's hasami-tsuke starts the reduction of Black's lower left corner.

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The Main Semeai continues.

; :
KataGo likes to play White's remaining kikashi "early".

Black must not play any reduction.

Just before her decision point, White will connect her single stone at the upper edge with . Black will force with for at the top, before occupying the last valuable point of in the right centre.

If she mistakenly waited until after her decision point, Black would not sacrifice the additional stone at in the Semeai Variation, so gaining one point therein.

Capture Variation:

Compared to Our Solution (2015 / 2017), ...

• White destroyed two points of Black's territory in the upper left corner.
• White got an additional two points of territory at the upper edge.
• Black destroyed one point of White's territory at the top.
• White's cumulated gain in the upper right corner is seven points.
• Black destroyed one point of White's territory in the right centre.

In total, Black lost nine points.

Black + 5 => White + 4

Semeai Variation:

Compared to Our Solution (2015 / 2017), ...

• White destroyed two points of Black's territory in the upper left corner.
• White got an additional two points of territory at the upper edge.
• Black destroyed one point of White's territory at the top.
• In the upper right corner, White got an additional four points of territory, but captured two Black stones less, so the net effect is zero.
• Black destroyed one point of White's territory in the right centre.
• White captured one Black stone more in the right centre, so gaining two points.

In total, Black lost four points.

Black + 3 => White + 1

After a short stopover in the world of amateurs, where they were advised to adjust their timing, we are back in the era of KataGo again ...

( 2032)
This is the position when Black played Harry's Hasami-Tsuke sequence , much earlier in the game.

: (A 2032a)
White's jump down to the second line starts one of KataGo's astonishing attacks at Black's upper left corner from the inside.

White might also start with the occupation of the Guzumi Point , later reverting to the sequence shown below.

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KataGo likes to play the final kikashi in the hanezeki early.

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Black's diagonal move restricts White's movements in the upper left corner.

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White tries to get access of the corner.

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Black occupies the vital 1-2-point in the corner.

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White's push at the left edge destroys two points of Black's corner territory without losing any tempo in the Main Semeai.

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Black is forced to connect immediately.

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White occupies the Guzumi Point in between.

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Black answers with Michael Redmond's Kikashi.

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White's solid connection keeps Black par with the Punishment Semeai Liberty Level.

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Black has no choice but to follow White with the Main Semeai.

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White's atari at the upper edge continues the fight in the upper left corner.

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Black prevents White from getting access to the corner.

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After this move, the formation at the upper edge resembles that after Yamada Shinji's Tsuke, but without White's sacrifice of her cutting stone at .

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White's hasami-tsuke starts the reduction of Black's territory in the lower left corner.

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KataGo likes to strengthen White's shape in the Guzumi Area in between.

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It is best for Black to tenuki to the upper left corner, as usual.

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Black must still play a protective move in the upper left corner, securing a sure eye at .

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The Main Semeai continues.

Black must not play any reduction.

Capture Variation:

Compared to the previous variation, ...

• White cumulated gain in the upper left corner is two points.
• Black's cumulated gain at the top is one point.
• Black destroyed two points of White's territory in the upper right corner.
• White captured one Black stone less there, so losing two points.
• White got an additional point of territory in the right centre.

In total, Black gained two points.

White + 4 => White + 2

Semeai Variation:

Compared to the previous variation, ...

• White cumulated gain in the upper left corner is two points.
• Black's cumulated gain at the top is one point.
• Black destroyed two points of White's territory in the upper right corner.
• White captured one Black stone more in the upper right corner, but one Black stone less in the right centre, so the net effect is zero.
• Black captured one White stone more at the left edge, so gaining two points.
• White got an additional point of territory in the right centre.

In total, Black gained two points.

White + 1 => Black + 1

2032

2022MainLine