This section is dedicated to KataGo's first new discovery, the Atari within the Nakade Sequence, which can be successfully played at only one moment in time.

We compare KataGo's new sequence around the nakade with Fujisawa Hideyuki's classical line of play, in order to identify the individual value of KataGo's Atari.

This is not so trivial as it seems, as there are some interdependencies with KataGo's other new findings, due to different effects of the various continuations on the Main Semeai Liberties.

Let's enter the world of KataGo ...

: ( 2022MainLine)
This move is KataGo's Atari at Black's single stone below within the (therewith updated) Nakade Sequence.

KataGo's atari is typical for the genius of Inoue Dōsetsu Inseki, because it can be played successfully only now.

For our detailed analysis of the timing of this atari, and Black's inability to resist, please refer to ...
1093a

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We follow the course of KataGo's initial version (2019) by strengthening Black's formation in the left centre.

Black is unable to capture White's single stone in the lower left with , instead.
White would throw-in at , and give double-atari at after Black captured with , so getting an independently alive shape on the left side.

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White is forced to connect.

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White's previous move was an atari, so Black has to complete the nine-stone nakade.

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Now, White captures Black's stone in the lower left.

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Black is forced to connect, defending his lower left corner.

Harry Fearnley suggested giving atari at , instead, aiming at initiating a ko-fight. However, this move will result in a change in the order of moves only.

White will continue with Yamada Shinji's Tsuke in the upper left corner.

Let's make a short detour to the dawn of time ...

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Since Fujisawa Hideyuki 9p, the Nakade Sequence has continued with the atari at Black's eight-stone group at the left edge.

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Black has to complete the nine-stone nakade.

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White captures the nakade "early".

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Later, during the process of the mutual occupation of opponent's liberties in the Main Semeai, Black will connect at .

Let's return to the world of KataGo ...

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White connects her single stone in the right centre.

Yamada Shinji's Tsuke can be played also later, in principle. We will do without here, in order to simplify the comparison with the classical line of Fujisawa Hideyuki.

Even if Black should be able to capture White's two stones in the lower left in the course of the Main Semeai, White would have already gained an advantage of two points.

In this case, the relationship of liberties in the Main Semeai would remain unaffected.

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Black gives atari at White's two stones in the lower left.

: ( 103 2036)
We continue with the Main Semeai first.

As a matter of course, White would benefit in the Capture Variation by connecting at , instead.

However, she would suffer a loss in the Semeai Variation (but which is irrelevant here in this line of play, as the Capture Variation is better for White).

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Black captures White's two stones.

Liberties:

Fujisawa Hideyuki (at left):

• Neither side played an additional move.

KataGo's Atari in the Nakade (at right):

• Both sides played two more moves (, ) locally.

No effect overall.

Please note that White's sacrifice of her two stones might be a valid but often overlooked option in cases, where the kikashi in the hanezeki have not yet been played.

Territory (in the Capture Variation):

Fujisawa Hideyuki (at left):

• Black has five points of territory in the marked area.

KataGo's Atari in the Nakade (at right):

• White captured one Black stone, so gaining one point.
• Black captured two White stones, so gaining four points.

= Three points in total.

White gained two points through the capture after KataGo's Atari.

VAR

: ( 2036)
If White connected her two stones, her local gain would increase to six points.

However, White lost two tempi in the Main Semeai by this connection.

Territory (in the Capture Variation):

Fujisawa Hideyuki (at left):

• Black has five points of territory in the marked area.

KataGo's Atari in the Nakade (at right):

• White captured one Black stone, so gaining one point.
• Black does not have any territory in the marked area.

= One point in total.

White gained six points locally through KataGo's Atari.

White's effective benefit will be smaller, however, because Black can - due his winning of two Main Semeai Liberties - partially achieve compensation on the rest of the board.

Liberties:

However, ...

White's connection costs her two tempi in the Main Semeai.

This effect on the relationship of liberties in the Main Semeai will enable Black to take some profit elsewhere on the board.

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Here, Joachim's Hiki of is the largest point on the board now, defending Black's large territory in the upper left corner. Thereafter, Black will win the game for sure.

It is therefore mandatory to start the endgame in the upper left corner earlier (either with Yamada Shinji's Tsuke or with Fujisawa Hideyuki's Atari ), preventing Black's hiki.
That will be the subsequent topic.

2036

Some time later in KataGo's world ...

This is the position of the main line after the "early" endgame on the left side of the board has stopped - for the time being.

It's White's turn now.

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Let's keep this analysis here (regarding KataGo's Atari) independent of the effect of KataGo's Bad-Shape Move and connect at in the right centre, instead.

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Black gives atari at White's two stones in the lower left.

: (A 2036)
White connects.

We will calculate the impact of this connection at the end of the subvariation below.

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Black's push at the top can be played at any moment, when Black is at least one over par with the Punishment Semeai Liberty Level.

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White is forced to connect.

If Black was par with the Punishment Semeai Liberty Level, however, White answer at , taking an important Main Semeai Liberty of Black's large group.
Even after giving atari at White's three stones below, Black would be unable to divide White's forces at the top.
White would choose and win the Punishment Semeai.

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Black is able to capture White's single stone at the upper edge, but loses one tempo in the Main Semeai through this move.

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White occupies a Black liberty here, in order to simplify the presentation.

Please note that only the result of the Semeai Variation will be affected through Black's taking profit outside the Main Semeai Area hereafter.

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Black's atari is sente.

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Black still has one Main Semeai to spend. He uses it for the connection of his two stones at the upper edge.

VAR

: ( 2036)
White continues with the Main Semeai, not losing any tempo therein.

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Black captures White's two stones in the lower left.

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White continues with the Main Semeai.

After her decision point, White will connect at . Thereafter, Black will play his kikashi , at the top.

Territory (in the Capture Variation):

Black captured White's two stones (at left):

• Black got four points of territory in the lower right.
• White got two points of territory at the upper edge.

= Two points for Black in total.

White connected her two stones (at right):

• Black does not have any territory in the lower left.
• Black captured one White stone at the upper edge.
• White does not have any territory there.

= One point for Black in total.

White gained one point by the connection of her two stones in the lower right (at right).

In total, White gained three points by KataGo's Atari in the Nakade Sequence.

2036

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