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Japanese Rules
    Keywords: Rules

Japanese rules are defined by the Nihon Ki-in:

Japanese rules:


Special Rulings

Because the Japanese rules make use of Territory Scoring, which penalizes plays in your own territory, special rulings have been devised so that a group can be pronounced dead without having to make further plays.

See Bent Four In The Corner for one example.

See also: QuestionAboutJapaneseScoring


BillSpight: The 1949 Japanese rules were widely criticized for its special rulings, which seemed to have an ad hoc character. The 1989 rules were an improvement in the sense that such cases are now decided by method. The drawback is that the method is not easy to understand, and still produces some unexpected and peculiar results.

TJ: As I understand it, current japanese rules are to play out any situation in dispute on a seperate board, with the only thing that matters being the life and death of the group in question. In other words, the only valid ko threat would be one local to the group in question. If the stones die, and are not replaced with live ones, the group is dead, and removed from the original board, and scoring continues. With the dead bent four, this would mean that the killer starts the ko, and any ko threats remaining, removable or non-removable, are irrelevant, and the dead bent four will be "found" to be dead. In most cases, both sides know dead bent four, so the dispute phase can be skipped, there being no dispute if both sides agree it's dead.

I don't understand how this is supposed to be difficult to understand, so I think I'm missing something here...could someone please tell me what I'm missing?


I am reminded of the following quotation from Tony Hoare:

"There are two ways of constructing a piece of software: One is to make it so simple that there are obviously no errors, and the other is to make it so complicated that there are no obvious errors."

--Matthew Woodcraft


Possible outcomes for games played under Japanese rules include at least the following:

  • Black wins, White loses
  • White wins, Black loses
  • Jigo
  • No result
  • Both players lose
  • White wins, but Black does not lose
Bill: I do not believe that the last is possible under the current rules, and occurred only once before Japanese rules were codified.

Matt Noonan: I've never heard of this before! Can somebody give a pointer to more information about "White wins, black doesn't lose?"

BobMcGuigan One such game occurred in 1928, I think, in a ranking tournament game between Segoe and ? (I can't remember the other player's name). It involved a 10,000 year ko which didn't get resolved. The referee decided the outcome of the game was that White won but Black didn't lose. It's a historical oddity that was a factor in prompting the development of official rules.

Charles Matthews See the ten-thousand year ko page for more about the Segoe-Takahashi game, and a link to John Fairbairn's article about it.



This is a copy of the living page "Japanese Rules" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.