(Referenced by 140; 155; 157; 243; 250; 418; 1018)

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With the main line of Joachim's Ko-Semeai after his sagari at (either with or without Michael Redmond's kikashi in the bamboo joint beforehand), we did not evaluate the potential number of Black's ko-threats on the left side so far. One reason was that White's partial group in the upper left corner has seven liberties (). Therefore, there are no ko-threats against this group available after Black connected the hanezeki's tail (Black's connected group has only five liberties), i.e. after White started the ko "late".

For the application with an "early" ko, we will calculate Black's ko-threats after White's moves from to respectively. Please note that White must be extremely careful with playing one of these protective moves on the left side, because she loses one move in the semeai sequence on the right, which may end futile.

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However, Black might try to close his top left corner - simultaneously pre-empting all of White's ko-threats in this area - hoping to return to the Main Semeai between left, and right, which he would win. White's upper partial group has five liberties only ().
Now, one option for White is to get life for her group on the left side, with any of the moves from to (most of these will also capture Black's group there), forcing Black to return to the ko-fight on the right side of the board. Then, the number of Black's ko-threats that remain on the left side will become decisive.

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In one case or the other, White's group may lose another liberty to be left with six liberties (), as exemplary shown here.

It may be a bit counter-intuitive, but we will see that the number of Black's ko-threats in not effected by this measure.

The following table gives a summary of the results of our detailed sequences that are given thereafter.

Move Page Seven Six Five Liberties
  844   2    2    6 (!)
  848   4    4    4
  851   2    2    2
  852   2    2    6 (!)
  854   7    7    7
  858   7    7    7
  861   6    6    6

With correct choice by White, Black cannot get more than two ko-threats only. You will recognise that is always best, and that , and , become worse with the massive reduction by two liberties (before White's kikashi there; five liberties remaining) in the top left corner.

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Black may consider to pre-empt the cases , , and , above by inserting the first one, or two, exchanges of the Nakade Sequence ( / ).

Please note that we assume White's group to have seven liberties, i.e. the main line of Joachim's Ko-Semeai, where White inserts her own kikashi in the upper left corner ( / ). Quite surprisingly, additional Black stones at , and , will not affect the calculation of Black's ko-threats in the nakade here.
The results are as follows.

Move  1^st /      2^nd /  
     3   848      2   850
     2   854
     6   855      5   857
     6   858      5   860
     5   862      4   863

Again, with White's correct choice, Black cannot get more than two ko-threats. With one nakade Exchange played, White must choose , with two moves of the Nakade Exchange, her choice will become .

Not very surprisingly, the cases , , , and , are reduced by one, respectively by two, ko-threats. Black simply lost some of his ko-threats therein with the partial Nakade Sequence.