thousand year ko
A.k.a. ten thousand year ko, mannen-ko. A configuration of stones where neither side may wish to start a ko because to do so can only be justified by a larger ko threat than that available. In the example shown, to start the ko, Black must first play at A capturing one stone, then play at B, but White can then recapture, meaning that black must make the first ko threat. Only if Black is certain to win the ensuing ko fight with enough threats, each of a sufficient size so that White will not ignore any one of them, will Black wish to play this way. Similarily, if White wishes to start the ko, he must first play at B, and then Black will capture the single white stone, meaning White must find the first ko threat of suitable size. Thus it is quite likely that neither player will disturb the position, leaving it alone for a very long time! At the end of the game, the situation is judged as a seki and under Japanese rules White is obliged to play at A. |
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