Dual ladder breaker

Chinese: 镇神头 (zhèn shén tóu)
Japanese: 鎮神頭 (chinshintou)
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...)

White to play. How to prevent two ladders?

This is the first ladder.

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

The dual ladder breaker is .

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

JoelR asked above: Does 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.