Lesson 2 - Crane's Nest Example

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Here's a reasonable position in which B is in dire straits, having had three stones cut, and a weak three stone group on the outside.

 

If B cuts, W can just atari. But what if W is afraid for this two stone group at 13 and 14, and doesn't want any of its liberties removed? Or perhaps the ladder doesn't work for W.

 

In that case, W may jump straight out, in which case we have the Crane's Nest situation. However, it is W's move, and the player can easily secure the three stones while putting pressure on B's two cutting stones by playing the following move:

 

This will connect W's group to the outside, B's three side stones are as dead as ever, and now B has two weak groups in the center achieving nothing. W will only save the three stones like this, though, if he or she anticipates the Crane's Nest tesuji. Otherwise, the W player might not realize that there is any danger - after all, the short jump is normally secure when extending from a three-stone base. If W fails to see the danger, B's three side stones will be alive, there will be no weak groups, and W will have three separated groups instead. The value of the tesuji is therefore tremendous.