Ja-Choong-Soo
Ja-Choong-Soo (자충수 Revised Romanization: Ja-Chung-Su, McCune-Reischauer: Cha-Ch'ung-Su) is a Korean go term. It literally means "self filling up move".
This is not meant to be definitive. I was reading Minue's HaengMa Tutorial For Beginners and he tries to define this at length. Being a literal minded fellow, while I can follow the explanation, the term itself did not make sense, until I thought about it some more.
So this is my own take on it, and hopefully will explain to other literal minded folks how to avoid the confusion. Perhaps others can bang it around with more examples, and maybe a good English phrase can be coined.
![[Diagram]](../../diagrams/37/b0a9be91435dab58d7c3f1e358260174.png)
Real game example (2): Black 3 as "ja-choong move, or self-atari move in broad meaning". Taken from Minue's HaengMa Tutorial For Beginners.
The beginning of the discussion starts with this joseki mistake. Typically, after , black will hane at a, white extends with
, and black will play at b to make good shape. However in this example, black makes a mistake and plays
. This is an example of ja-choong-soo, a self filling up move.
The idea of a move that reduces its own liberties is a bit odd until one realizes two things. First, you have to take the response into account. The obvious move here is which completes the tiny local position. The second is that there should be a net growth for each move.
The black 3-4 stone has 3 liberties after the attachment. The two black stone group has three liberties after . Literally, there is no reduction in liberties. However, if we consider that a simple iron pillar increases liberties from 4 to 6 with the addition of the second stone, we can see that the second stone in the example mistake is a net decrease in liberties comparitively.
Basic Example
Example from this baduk site
is a really stupid ja-choong-soo (except maybe as a losing ko threat), because it destroys the seki.