Throw-in ko

Throw-in for ko  

In the endgame Black can throw in at and start a ko here. First Black plays , and White must take with .

Continuation  

Then Black plays and White is in no position to connect. White has to start the ko by capturing . It is however hard for White to resist: large threats are required.

Black's ko victory  

Black has a follow-up at a which is substantial, once Black has captured to win the ko (marked stone). If White just connects at a Black has of course taken profit in sente here (and then can return to answer White's threat).

No profit  

Simply playing here makes this area all neutral points, which is much inferior for Black.

--Charles Matthews

Like a 10,000 year ko  

Black makes a throw-in at to make the ko. White could make the ko with a throw-in at . Black could also make seki by playing instead of .

This position is like a ten thousand year ko because whoever makes the ko, the opponent takes it first, and one player can make seki.

Black can change his mind about the seki and make a ko by sacrificing three stones. See Sending Three Returning One.