L+2 group with descent

L+2 group with short-side 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.

continued  

White's best response is , leading to a two-stage ko. White uses capture at a as a local ko threat. (Though some English books suggest at throw-in immediately, it needs another approach move at .)

When Black wins the ko  

When Black wins the two corner 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... :-)

with short-side descent  

It is worthwhile to discuss this variation. This leads to a direct ko with Black taking first, so is inferior to the main line. is the only move to avoid seki.

L+2 group with long-side 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.