Dual ladder breaker

    Keywords: Tesuji, Tactics, Problem

Chinese: 镇神头 (zhèn shén tóu)
Japanese:
Korean:

A dual ladder breaker or double ladder breaker is a move which breaks two ladders at a time.

Examples can be found in difficult TsumeGo-probles such as Igo-Hatsuyoron #6?, or actual, famous historic games (e.g., see the first recorded dual ladder breaker), not to be forgotten the variations from Joseki-variants (e.g., 2-4, two-high-kakari, outside-attachment...)

[Diagram]

Problem

White to play. How to prevent two ladders?

[Diagram]

Ladder 1

This is the first ladder.

[Diagram]

Ladder 2 (8 at 1)

This is the second ladder. If W6 at B7, then B7 at a, and eventually White will still need to capture at W6.

[Diagram]

Solution

The dual ladder breaker is W1.

[Diagram]

Discussion

Technically it does break the 2 ladders, but now a and b are miai as they are both double atari. So this probably isn't a good example. ~srn347

Both a and b were double atari before, but the white+circle stones are not that important. Breaking the ladders keeps the black+circle stones dead, which gives White a big corner. Does c not break both ladders also? -JoelR


[Diagram]

Other attempts

JoelR asked above: Does W1 not break both ladders also.

No, it does not. B can threaten one ladder and then capture some stones in a squeeze. There are probably other ways for black too.

[Diagram]

Other attempts - contd.


See also:


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