British Go Journal No. 55.  March 1982. Page 21.
This article is about how to capture stones. Dont expect wonders from knowing the right way to capture, it doesnt make a lot of difference. For years I had never noticed that there was a right way and a wrong way until finally I was shown the error of my ways after a cafe game in Switzerland some months ago.
Diagram 1 |
I have kept the example very simple, though the principle applies in lots of different positions. Look at Dia 1, Black is to play and capture two white stones. Should he play A or B? Whichever he plays, White C will be sente. However White wont play C straight away because it is a potential ko threat.
Diagram 2 ||
Diagram 3 |
If you look at C as a ko threat then the difference between A and B becomes much clearer. Dias 2 and 3 show the positions after the ko threat C has been ignored and White has captured two stones. A gives Dia. 2 where White has captured the stone and can play the hane and connection at 1 and 3 in sente. All this adds to the size of the ko threat. If Black had played B then the position after he ignores Whites ko threat is Dia 3 where white gets no more points in sente.
So if Black plays A the ko threat he leaves behind is four points bigger. The principle is always to play from the inside B rather than the outside A in positions where you are catching stones on the edge. The difference will rarely be exactly four points in the size of the ko threat but it will always be at least two because of Whites capture of the stone.