L+2 group with descent

L+2 group with descent  

It is said that the L+2 group is alive. However, when there is a descent at , it is not exactly the case.

The tesuji

The tesuji  

The tesuji of and exploits the stone.

White's mistake  

What works for the L+2 group case does not work here. The atari at is a mistake. After , due to shortage of liberties, White is unable to prevent Black from connecting the three stones at a.

White's best response  

White's best response is . Black can play either a or b.

Method I: What many books say

What many books say  

Many books suggest making the throw-in at directly. This is a two stage one move approach ko.

The approach move  

The required approach move is , converting it to a direct two stage ko.

The two stage ko  

For White to win the ko, he must make two moves at and .

The two stage ko  

For Black to win the ko, he must make two moves at and connect at .

Method II: A better method?

Hane first  

Bill proposed that Black can hane with and start a ko with . This is a two stage ko for Black, and White has a ko-threat at a. In most cases, this method is slightly better than the previous method.

When Black wins the ko  

When Black wins the two kos, Black connects at to finish White off.

Alex: Looks like a good way for a Moonshine Life position to arise. Now White just needs to arrange for a double ko somewhere else... :-)

Method III: When both sides have no ko threats

What many books do not say  

When neither side has a ko threat, this is best. Note that both players threaten to make a ko. This is like a ten thousand year ko, either player can convert to a proper seki.

L+2 group with descent  

The descent at does not affect the status of the group, which means that White is unconditionally alive. Defence against Black's attacks are identical to those listed in L+2 group.

L+2 group with descent  

It is worth while to discuss this variation. The ko is White's best result, but inferior to the main line. is the only move to avoid seki