British Go Journal No. 1.  Summer 1967. Page 7.
(This is the first of a series of articles for beginners and players of average strength written a few years ago by the Editors of the American Go Journal. The fundamentals of Go strategy and tactics will be the subject and the style will be basic, assuming no previous study.)
This first discussion concerns the plays which extend armies towards the centre of the board. Such plays are usually called for at the end of the opening stage and throughout the middle-game. One extends to the centre for many reasons; to rescue armies without eyes, to surround enemy groups, or to secure a portion of the centre. Generally, the player who dominates the centre is able to connect his armies, simultaneously dividing and constricting the enemy.
If one player extends too timidly toward the centre, his opponent may seize the vital points; but if he jumps too boldly, he may find himself cut off from his base. He must also bear in mind the need to consolidate his extensions sooner or later, converting all gaps into solid connection. Waiting one move too long for such precautions can be fatal. Some further clues to these distinctions will be found in what follows.
Eventually, all connections must be resolved to solid connections along a straight line, and this is, therefore, the only "true" connection. All other positions can only be potential connections, depending on certain conditions to become true connections.
Diagram 1 |
The "diagonal" connection or "Kosumi", is close to a true connection, and may be considered a "virtual" connection. But many players forget that a play at A or B in Dia 1 is needed to make this a true connection.
With this warning in mind, we can proceed to examine the most common ways of extending toward the centre.
Diagram 2 ||
Diagram 3 |
The first extensions toward the centre will usually be made in the course of corner play, in close or direct contact with enemy stones. The solid extension occurs most often in response to direct contact: Dias 2 & 3 are both good examples of this.
Diagram 4 ||
Diagram 5 ||
Diagram 6 |
The kosumi has a left or right directional purpose, as shown here. A kosumi is usually seen when opposing stones are in the near vicinity or on both sides; ideally, the very compactness of this play is a threat. Dias 5 & 6 show common situations where the kosumi has potential strength in two directions.
Diagram 7 ||
Diagram 8 |
Many other forms of virtual connections are used in extending under pressure. The "bamboo joint", Dia 7, is a very strong formation which might be used more. The only limitation of this strong connection is that it is subject to a ko threat, but its tactical advantages are plain.
When extending from a pair of stones the single skip to 1 or A in Dia 8 serves as a virtual connection. There are many forms of safe connection, and it is important to choose the most aggressive of these; a well-placed extension will often wrest sente from the enemy. It would be tempting to draw up a chart of such extensions, but the dangers of learning by formula are great. Beyond the basic example, each situation must be analysed by the player himself.
When extending in open situations, without the pressure of strong opposing formation, it is normal to extend a step further than the "virtual" connection. The purpose of such moves is not to insure a connection, but rather to move boldly to gain territory and influence in such a way that attempted cut would be unprofitable.
Diagram 9 |
A great deal of attention should be paid to the single skip for this is the normal form of extension to the centre. An example of a fuseki situation built up entirely of single skip moves is Dia 9. When Black plays 1, threatening to surround a vast territory, White invades lightly with 2. Then Black defends with 3, and White retreats to the centre with 4. Black then presses down on the other White position with the L-shaped formation of 5.
Diagram 10 ||
Diagram 11 |
Why is the single skip used so often? Its strength lies in its versatility. Consider the single skip in Dia 10. Note that White can play between the stones and Black has no immediate prospects of capture after this sequence. He can develop the situation with 6' at A, if elaborate in-fighting will be profitable to him. Or on the other hand, he can sacrifice the original stone to build territory or influence in the centre. Dia 11 is one such line of play in which Black can dominate the situation and still keep sente. He might equally well have built the same formation in one of three other directions.
What are the limitations of the single skip? When is it vulnerable?
Diagram 12 |
When the enemy has built up strength on both sides of it, such as Dia 12 Black must now protect against a cut at 5. White can connect through the Black position as shown if Black doesnt reply. A play at 4 or 6 is often seen as a guard against this. Generally, any horizontal or diagonal play can be used to convert the single skip into a virtual connection.
A series of single skips towards the centre is usually neither more nor less vulnerable than one, and a chain of such extensions is often seen. The L-shaped formation in Dia 9 is also often seen. Here Black threatens to attack at A; but once White defends Black is vulnerable to a play at B, and should watch this point carefully.
Diagram 13 ||
Diagram 14 |
The keima is a weak link for beginners, who may not realise that it has little connecting value. The stronger player bides his time, than attacks these links later in the game. To prevent such a cut at A or B Black must be able to capture by a ladder in either direction - and relying on such ladders can be a source of more weakness than strength.
What is the proper function of the keima?
Not as a connection nor as an extension to the centre, but rather as a surrounding move, bearing heavily to left or right. In Dia 14, the keima at 1 is a good surrounding weapon. Here Black is not at all worried by a White cut, for White himself cannot avoid being cut off, and if Black has any kind of leeway to left or right the White stones will die. Thus the keima is an attacking rather than a defensive play.
There are two basic situations which govern extensions toward the centre. When opposing men are in close contact, or have strong influence nearby, the solid or diagonal extensions are often used. Other forms of virtual connection are also used that cannot be cut in the general course of play.
In open situation, the single skip is the normal extension. When planning such an extension the beginner should not only ask himself, "Can this be cut?" but also "If White cuts, how shall I answer?" If there are no White stones nearby to support such a cut he can proceed boldly to make the normal extension without fear of the consequences.
Part 2 is on page 23 of Issue 2 .