Xuanxuan Qijing Problem 43: Black to play and make a ko
玄玄棋经 · Problem 43 of 347 · Sacrifice on the 1-2 point
White's corner looks safe and Black has no obvious way in. Look for a sacrifice on the first line that White cannot simply capture.
How to solve it
White's corner looks safe, and Black seems to have no way in. The hidden resource is the sacrifice at A18, the 1-2 point.
White's only defence is C17. Black then captures a stone with B17, and the result is a ko.
If White captures the sacrificed stone with A19 instead, Black plays C18. After White's D18, Black's D17, White's E17, Black's C17 and White's B17, Black's C19 leaves White short of liberties on both sides, and White dies without a ko.
Main line
- 1. Black A18
- 2. White C17
- 3. Black B17
Solution checked against Sensei's Library.
Play it out on the board
Place the stones yourself and see the refutation when you miss. All the Xuanxuan Qijing problems as quick lessons.