Ko Problem Solution

Welcome back! Lets start by looking at the problem again and then see how the problem developed before looking at the solution:

Dia. 1

Black pushes at 1 to gain a few points in sente and then plays at 3 to reduce white's influence. The 1-2 exchange is actually very bad for black. How does white take advantage in the corner? Once you figure it out, and I mean figure it out, if you don't start practicing your reading sometime you'll never get better, then go ahead and read on. Go ahead and lay it out on a board and look at it for a while if you have to. A strong kyu player should be able to spot this quickly, a dan player should see it instantly. There are only so many combinations in a small corner situation like this and even a weaker player should be able to lay it out on a board and go through it till they find the answer.

To see how this diagram came about we have to see how this invasion happened. It starts with black's probe at 1:

Dia. 2

Depending on how white responds this could go many different ways but white plays at 2 which is a simple response that stresses the outside. Black hanes at 3 and through 7 is unconditionally alive in the corner. Later white can play this sequence to further seal black in:

Dia. 3

Note that on an open board white's influence far, far outweighs black's meager corner but this probe would not be played in the opening, it would be a middlegame tactic that might be used to rob white of the corner territory. As is usual the benefits of this trade would have to take the whole board into account. Back to our problem though, did you find the ko?

Dia. 4

By pushing at 1 black reduces his own liberties, now it becomes imperative to reinforce the corner which makes black 1 a very small gote move. Since black foolishly tenuki's at 3 white strikes at the vital point at 4 (note how black plays at the same point in Dia. 3) and after the 6-7 exchange where black makes an eye white throws in at 8 to create a ko. Since without 1 black is unconditionally alive this has turned into a terrible exchange for black.

Next time we'll follow up on that Shusaku game that I started analyzing. Have fun!