Joachim's Ko-Semeai - Putting the Cart
Before the Horse (2013 - 2015)
4b - White Starts the Ko "Early"
( 980) (Referenced by 140) What about the "early" ko for White? This will be White's last hope for success in the sub-variation with . Let us assume that Black did neither play the three hasami-tsuke moves in the upper right ( / ), nor the throw-in in the centre ( / ). |
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: !!! Let us further assume a "very early" start of the ko-fight by White, combined with a "peaceful", and "uncomplicated", continuation (this means that White will not pre-empt any of Black's ko-threats shown). !!! |
White has allowed Black to get all the moves - as ko-threats, which he kept in reserve. Additionally, White allowed Black's larger eye, with the / moves. We suppose that we are on the "safe" side with our analysis, when we give Black (nearly) everything that he wants to have. |
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In principle, there is the Hanezeki Exchange of / left, and you might wonder, whether Black might get another ko-threat there (which would be the key for winning). White needed to play the two move-pairs of / , and / . Let us assume that the ko-threats are independent from each other (what they are not really in the problem). Even if Black starts the exchanges (what he really did in the sequence above), we will get the following sequence (exemplary; you might interchange the Black moves as you like): / / / / / (pre-empts a Black ko-threat) / . Black is unable to get all five of "his" ko-threats. Please note that it is White's turn now. This implies that White could "steal" Black another ko-threat, if there was any. This means that Black really needed seven ko-threats, versus White's two, for success with the "early" start of the ko-fight. |
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: Black's earlier move at destroyed the connection of White's -stones, but left White's group with two outside liberties (one more than without ). But Black got an additional ko-threat at , so the resulting effect is Zero. |
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: Black's initially played move, at , assumed to benefit Black through hurting White's shape on the upper edge, eventually provided White with a decisive advantage. It is difficult to decide, whether Black should have chosen the main line of Joachim's Ko-Semeai, instead, because here White is forced to encounter a long ko-fight that started "early". |
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