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2.3.2 Connecting a Final Ko

Historically, this question arose in July 1948 in the first game of a ten-game match between Go and Iwamoto. The question is whether Black, who has more ko threats, has to play 1 or 2 in Dia. 2-4. The decision at the time was that White had won by "one or two points," but this unprecedented decision was later modified to state that White had won by one point, because it was found that the provisional Nihon Kiin rules then in use said, "When one player has more ko threats, that player does not have to eliminate a final ko at the end of the game." Still later the Nihon Kiin enacted its 1949 laws, according to which, "Reinforcement is required in a position that immediately becomes a direct ko." If that ruling is followed in the game between Go and Iwamoto, White wins by two points.

Dia. 2-4

Consider the simpler final-ko question in Dia. 2-5. There are no neutral points, and Black obviously has more ko threats. If it is White's move, White will either pass or play inside his own territory. If White plays inside his own territory then of course he loses a point, so Black can connect at 1 without suffering a net loss.

Dia. 2-5

What if passing is allowed? This can be divided into two cases: one in which a pass is regarded as a ko threat, and one in which it is not. The 1949 Nihon Kiin Laws do not fully cover this point, but their philosophy is close to the idea that a pass is not a ko threat. I agree that a pass should not be treated as a ko threat, because if passes are allowed as ko threats, repetition of the same position will occur.*

If we take this position, then when White passes in Dia. 2-5, if Black also passes, White still cannot play 1. The game therefore ends and the point at 1 becomes Black's territory.

Under the 1989 Japanese Rules of Go, Black needs to reinforce at 1 or 2 in Dia. 2-4, and at 1 in Dia. 2-5


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