Oshi-Tsubushi

  Difficulty: Beginner   Keywords: Life & Death, Go term

Chinese 1: 胀牯牛 (zhang4 gu3 niu2)
Chinese 2: 胀死牛 (zhang4 si3 niu2)
Japanese: 押し潰し (oshi-tsubushi)
Korean:

[Diagram]
Oshi-tsubushi  

B1 is oshi-tsubushi, literally "squashing push", a Japanese term (also used in English, but in English it is called internal liberty shortage by Robert Jasiek) for a life and death tesuji. The everyday translations, crush, squash, and smash, are also occasionally seen.

After B1, White's connection at the marked point is an illegal suicide move under most rulesets. Later Black can capture the two White stones, gaining two eyes and life.

[Diagram]
Self-capture as ko threat  

Under rulesets which allow self-capture, W2 is possible; the three White stones are then immediately removed. If White can play at the W2 point it would kill the black stones. B2 now makes life, and so because Black must respond to attain it, the self-capturing move can be used as a ko threat.

[Diagram]
Black instead tries to play ko and dies  

If Black misses the oshi-tsubushi and instead takes the ko with B1, White plays under at W2 and Black will die. Taking with B3 is useless; White throws in with 4 at W2 and Black only has a false eye here. (If instead of W2 White mistakenly treats this as a ko fight, making a ko threat and then retaking the ko, Black gets a second chance at oshi-tsubushi.)

[Diagram]
White to play and kill  

If White to play in the original position, he can kill Black by connecting at W1 and forming nakade. If B2 captures the three stones, White 3 at W1 holds Black to one eye.

[Diagram]
Damezumari prevents oshi-tsubushi  

Oshi-tsubushi can be prevented by damezumari. In this position, Black's lack of liberties means that after B1 he is still in atari.


[Diagram]
Typical problem  

W3 here doesn't understand the position. Now Black can live.

[Diagram]
Black 4 lives  

Black lives with the sacrifice B4 and oshi-tsubushi at B6.

White should have recognised that this is a bent four in the corner position and played at B4 himself.


See also:


Oshi-Tsubushi last edited by 24.91.93.132 on February 27, 2015 - 21:18
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