British Go Journal No. 17.  June 1972. Page 7.
The object of this article is to examine the necessity for and effect of connections in yose made on the first and second lines.
Diagram 1 |
Diagram 2 ||
Diagram 3 |
Dia 1. This is a simple problem. It is obvious that, after white cut at 1, black is in trouble. Black should have made a connection. The two connections shown in Dias 2 and 3 readily spring to mind, but there is a difference between them. The connection of Dia 2 is a solid connection, but that of Dia 3 is a hanging connection. The difference is that white could play A in Dia 3 as a ko threat. This may seem trivial, but in a ko fight every threat is important. Therefore, as we don't know what may happen later in the game, we should always connect as in Dia 2 to avoid this extra ko threat.
Diagram 4 ||
Diagram 5 ||
Diagram 6 |
On the other hand, a hanging connection may be used to avoid further complications which would otherwise arise, as in Dia 4. Following black 1, white A will be gote. A solid connection as black 1 in Dia 5 would be bad, as white 2 and 4 reduce black's territory by a further point and retain sente for White. Moreover, if White plays 2 as in Dia 6, the corner will become seki and white will even emerge from the exchange with sente.
Diagram 7 ||
Diagram 8 |
Diagram 9 ||
Diagram 10 |
In Dia 7, Black has played 1 and 3 with the intention of next
playing A. Is this good or bad? When the frightening possibility of white
4 and 6* in Dia 8 is considered, it is clear that a play at A is
dangerous. Instead of playing 3, as in Dia 7, black would do much better
to quietly connect at 1 in Dia 9. If white decides to invade with 2,
black 3 secures his position. A play such as black 1 in Dia 10 should
not be made, since the same situation as in Dia 8 arises and black will
be hard pressed to save his group.
* [BGJ had white 4 and 8.]
Diagram 11 ||
Diagram 12 |
Dia 11 shows a very common end game position. Black 1 sagari  is the correct
play. Should black connect as in Dia 12, white 2 and black 3 result in
the loss of an extra point. Beginners sometimes tend to play 1' at 3 and
then white can play 2 to create a ko if he so desires.
* [BGJ phrased the last sentence differently.]
Diagram 13 ||
Diagram 14 ||
Diagram 15 |
Diagram 16 ||
Diagram 17 |
From what we have seen so far, black 1 in Dia 13 seems to be correct. Black's alternative connection at 1 in Dia 14 is not so good. However, black would do better to play 1 in Dia 15. This is an excellent move as it reduces the advantage of white A, thus protecting two weak points at once. If black makes the solid connection, white can play 2 and 4 as in Dia 16, reducing black's corner and keeping sente. White 1 to 5 in Dia 17 are of no use because of Black . Following white A and black B, black will emerge from the exchange with sente.
Diagram 18 ||
Diagram 19 |
Finally in Dia 18 black 1 is the only correct play to save the group. Black 1 in Dia 19 invites white 2 and black can only manage a ko with 3.
It will be seen therefore that seemingly insignificant plays at the edge of the board can have considerable importance, and merit some care and attention.