# Under the Stones Problem 4 / Solution

Ko

is the only move. is the crucial defense in this problem. The result is a ko.

Continuation 1

Suppose is a ko threat that black answers with . Then after retakes the ko, black cannot kill by playing under the stones with .

Continuation 2

And white is alive because of his second eye at a.

White's resistance is not enough

is not the best move. under .

Failure

here fails, as white lives after and .

Authors

Discussion

Ko threat

Variations of reply #1

If Black replys to ko threat at then White takes ko and Black has to find the big ko threat to force White's response and then retake ko.

Variations of reply #2

If Black ignores the ko threat and takes with , then .

If @ b then @ c, and if attacks on top at e or f, then at a captures the four Black stones with the double cut; and if connects on the bottom then at f gets the second eye.

If on top at d, e, or f, then still at c, Black connects on the bottom at D-1 or F-1 to protect against the double cut, and at b makes White's second eye. (In the case of at e white may fill to protect and threaten the cut at f making f and b miai for the second eye.)

Under the Stones Problem 4 / Solution last edited by 118.201.183.142 on April 18, 2023 - 14:34