(;
AB[db][eb][gb][gc][gd][hb][cc][ec][fd]
AW[da][cb][ib][bc][dc][dd][hc][hd][he][jc][ed][fe][ge]
C[Black plays.

Source:
Go World #28, pp. 49-52, Summer 1982
"Basic Fighting Techniques"
Miyazawa Goro]
(;
B[ha]
C[This descent is a good eye shape move, but ...];
W[fa];B[fb];W[ea]
C[... after White connects out, Black has no way to make a 2nd eye.]
)
    (;
    B[bb]
    C[This atari seems like a good way to create aji in the corner, but ...];
    W[cd];B[ba];W[ha]
    C[... again White can ruin the eye shape.];
    B[ca]
    C[Black can start a ko, but Black can do better than this result.];
    W[ab]
    )
    (;
    B[cd]
    C[The following moves show why this nice move works.

This tesuji appears in all the old classic problem sets.];
    W[ce];B[bb]
    C[With the 2 marked stones, this atari will now give Black an important sente move.]
    TR[cc][cd];
    W[bd];B[ba]
    (;
    W[ha]
    C[If White hanes here, ...];
    B[ca]
    C[... Black's atari now threatens to make an eye without a ko.];
    W[cc];B[ab]
    C[Black has 2 eyes.]
    )
        (;
        W[cc]
        C[White can prevent the eye in the corner, but ...];
        B[ha]
        C[... but now Black can make 2 eyes along the top edge.];
        W[fa];B[fb];W[ea];B[ca]
        )
    )
)

