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GoTerms

 

Oiotoshi
Path: Tesuji   · Prev: ThrowIn   · Next: EyeStealingTesuji
  Difficulty: Beginner   Keywords: Tesuji, Tactics, Go term
  1. Oiotoshi describes a situation where a stone or group of stones is put into atari in such a way that there is no escape. This occurs usually when the only way to save such a group is to connect, and that the resulting group is still in atari.
  2. The term oiotoshi also describes the process of setting up such a situation.

Here's an example (modified from The Second Book of Go):

[Diagram]
Oiotoshi

B1 starts the oiotoshi. If White tries to run away at 2, Black 3 is atari again, and this time running away at 4 doesn't help White at all since now the whole group is in atari at a.

So White shouldn't have run away at 2, but instead connected at a or 4.



[Diagram]
Oiotoshi tesuji

Using the previous example as reference, it is easy to see that if White saves her two WC stones here, Black can capture WS, blocking off White's progress along the top side. B1 can also be called oiotoshi. (I'm not sure whether this example is relevant enough (and correct)! Comments, please. -- Jan)



BillSpight: B1 is premature. It requires the atari play BC below.

[Diagram]
Oiotoshi tesuji


I don't think this is premature. Doesn't this work? (Thomas Nordhaus)

[Diagram]


Bill is right, in the starting position the tesuji is premature and brings almost nothing. (Capturing one stone will be a bigger sente than if 1 hadn't been played, but on the other hand, one ko threat has been lost.)

White should of course connect at W4 and Black can capture only one stone which he can capture without sacrificing at B1 anyway.

-- AlainWettach

[Diagram]


Bill:

[Diagram]
Normal play

After Black 1, White 2 is White's correct response. If White does not play there, Black can throw in at 6. After White 2, Black 5 and White 6 are miai. Black can count 1/3 point in the ko (1/3 of the marked stone).


[Diagram]
Black error

White 6 fills at 1.
In this case Black has lost 1 point for the throw-in stone at 1, and does not have 1/3 point in ko. Black 1 gives away 1 1/3 points.



Oiotoshi is also known under the terms connect and die and serial atari.

See also: Damezumari and throw-in. The Crane's Nest is a classic example of oiotoshi.

-- Jan de Wit



Path: Tesuji   · Prev: ThrowIn   · Next: EyeStealingTesuji
This is a copy of the living page "Oiotoshi" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.