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Ladders

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Ladder
Path: Tesuji   · Prev: Snapback   · Next: Net
  Difficulty: Beginner   Keywords: Tesuji, Go term

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

Example

[Diagram]
Ladder

Black B1 starts a ladder to capture the WC stone.


[Diagram]
Playing out the ladder

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

Clearly White should see this and not play W2.



[Diagram]
A long ladder

Ladders may span a large part of the board. If for example Black captures the white stone in a ladder with B1, the ladder will go all over the board if White tries to escape, resulting in the next diagram.


[Diagram]
A long ladder

If White tries to escape, the ladder will continue 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 ladder from working is called a ladder-breaker.



[Diagram]
Ladder-breaker points

A simple technique for reading a ladder is to see six diagonal lines from the start of the shicho.[1] 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 ladder-breaker.

However, if there are both black and white stones on the marked points, please read the ladder 'manually': visualise it on the board. That's not so hard, either.


[Diagram]
Not a ladder-breaker

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


[Diagram]
Not a ladder-breaker

This diagram shows why - on the second line, White can play at W5 instead of d in the diagram, rendering the BC stone useless.

The reader might want to figure out why having a black stone at b or c in that diagram doesn't make a ladder-breaker.

Besides, note that the ladder-breaker points I have marked don't include the points on the first line. Go and figure which of these points make ladder-breakers, and which do not.

--unkx80



[1] Dieter: Kageyama says: No shortcuts. Read the ladder. Always. See Practicing Reading Out Ladders.


See also:



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This is a copy of the living page "Ladder" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.