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Shicho
Path: Tesuji   · Prev: Snapback   · Next: Geta
  Difficulty: Beginner   Keywords: Tesuji, Go term

A ladder (Japanese term shicho) is a technique of capturing stones. At each step the attacker reduces the defender's liberties from two to one.

Example 1

[Diagram]
Diag.: shicho

Black 1 starts a ladder to capture the marked white stone.


[Diagram]
Diag.: playing out the shicho

If White tries to escape, Black can at each time play atari and White will be captured.


[Diagram]
Diag.: A long ladder

One thing that is important regarding shicho is that they may span a large part of the board. If for example Black captures the white stone in a shicho with 1, the shicho goes all over the board if White tries to escape, resulting in the next diagram.


[Diagram]
Diag.: A long ladder

If White tries to escape, the shicho will go on in this way. Of course, as it stands, this is a disaster for White. But if there had been a white stone at a, White could now capture a stone and would stand to capture more because of all the double ataris that White can play. Such a stone which stops a shicho from working is called a 'shicho-atari' (English term 'ladder breaker').



[Diagram]
Diag.: Shicho-Atari Points

A simple technique for reading shicho is to see six diagonal lines from the start of the shicho. Unfortunately SL does not permit me to draw lines, so I have to make do with marking all the points instead. Except for a, b and c, any black stone (only) on the marked points will make a shicho-atari. However, if there are both black and white stones on the marked points, please read the shicho manually. It's not that hard either.

(Remark by Dieter: Kageyama says: No shortcuts. Read the ladder. Always. See also: Practicing Reading Out Ladders)


[Diagram]
Diag.: Not A Shicho-Atari

Why is a black stone at a in the previous diagram (the marked stone here) not a shicho-atari?


[Diagram]
Diag.: Not a ladder-breaker

This diagram shows why - on the second line, White can play at 5 instead of d in the diagram, rendering the marked black stone useless.

The reader might want to figure out why having a black stone in b or c in that diagram doesn't make a shicho-atari. Besides, note that the shicho-atari points I have marked doesn't include the points in the first line. Go and figure which of these points make shicho-ataris, and which are not.

--unkx80



See also:



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