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2007-11-05

Problem diagram.
Black's response to White's marked play?

Source:
Go World #38, Winter 1984-85, pp. 15-16
29th Honinbo, Awaji Shuzo vs. Rin Kaiho

Solution follows (or click here to download SGF)

Correct.
Black needs to force with 1 here first, but in the game Awaji simply forgot to play this key move from the joseki books! Black expands his space with 3, and then goes back with 5 to take the corner. Through 10 is a fair trade between Black making profit in the corner, and White building thickness.

A mistake.
Awaji (black) forgot to play the correct order of moves! White should have taken the key point with 2. If Black tries to save the 2 stones with 3, through 10 White is quite satisfied.

Black variation.
Black would more likely play 3 here, offering up the 2 marked stones, to avoid the previous diagram.

Numerous possibilities exist, but the result is the same, viz., White's corner lives and Black is left with a weakness somewhere on the outside.

So sometimes trusting the joseki books, assuming you know what's in them, is a good plan!

Game line.
In this game line, White misses an opportunity by playing 2.

The funny thing is that Rin, who knew that Black's previous move was not joseki, feared that Black had a secret prepared variation! So Rin played 2 here, in spite of knowing the joseki books' punishing response to Black's misplay at 1! Through 11 the game safely transposes into a "joseki" position similar to the first diagram above.