Go strategy and tactics
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The game of Go has simple rules and can be learned very quickly, but the immense amount of depth and complexity in the game that evolves from such rules has resulted in a variety of strategy and tactics to be developed over the course of history.
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[edit] Connection and separation
One of the fundamental strategies of Go involves keeping stones connected in groups. Connecting individual stones into a single group results in an increase of liberties. For instance, a single stone played in the center of the board has four liberties, while two adjacent stones in the center of the board form a unit with six. To capture the unit, an opponent would have to play stones on all of its liberties. Thus connected stones are stronger because they share their liberties.
Since connecting stones keeps them secure, an important offensive tactic is to prevent the opponent from connecting his stones, while at the same time keeping one's own stones connected. This act of dividing the opponent's stones into separate groups is called cutting.
While one should generally try to keep one's own stones connected, situations exist where doing so would be a wasted move. Stones are considered tactically connected if no move by the opposing player could prevent them from being connected. A common example is the configuration of stones in the shape of a "plus" sign. Although none of the stones actually connects to any other stone, they are tactically connected because an opponent playing in any of the available liberties would have no effect on the progress of play.
In a handicap game, Black starts with one or more handicap stones played before White's first move. If played in the traditional places on the fourth line from the edge of the board, these stones will mainly be useful for the purpose of connection and separation of stones played closer to the edge ("lower"). The White player's stones are threatened immediately with separation, while Black has many potential connections to begin with.
An example of inefficiency or poor coordination of stones in the context of connection is the empty triangle, where a stone has been played to connect before it is necessary.
[edit] Life and death
Main article: Life and death
A key concept in the tactics of Go, though not part of the rules, is the classification of groups of stones into alive, dead or unsettled.
At the end of the game, groups that cannot avoid being captured during normal play are removed as captures. These stones are dead. Groups can reach this state much earlier during play; a group of stones can quickly run out of options so that further play to save them is fruitless, or even detrimental. Similarly, further play to kill such a group is often of no benefit (except when securing liberties for an adjacent group), since if it remains on the board at the end of the game it is captured anyway. Thus groups can be considered "dead as they stand", or just dead, by both sides during the course of the game.
Groups enclosing an area completely can be harder to kill. Normally, when a play causes an area completely enclosed by the opponent to become filled, the group filling the area is captured since it has no remaining liberties (such a play is called "suicide"). Only if the last play inside the area would kill the enclosing group, thus freeing one or more liberties for the group that filled the space, can the play be considered. This can only be achieved if the liberties on the outside of the enclosing group have been covered first. Thus, enclosing an area of one or more liberties (called an eye) can make the group harder to kill, since the opponent must cover all of its external liberties before covering the final, internal liberty.
From this, it is possible to create groups that cannot be killed at all. If a group encloses two or more separate areas (two or more eyes), the opponent cannot simultaneously fill both of them with a single play, and thus can never play on the last liberty of the group. Such a group, or a group that cannot be prevented from forming such an enclosure, is called alive.
Groups which are not definitely alive nor definitely dead are sometimes called unsettled groups. Much of the tactical fighting in Go focuses on making one's own groups live, by ensuring they can make two eyes, and on making the opponent's groups die, by denying them two eyes.
[edit] Reading
Determining ahead of time whether a group is currently alive, dead, or unsettled, requires the ability to extrapolate from the current position and imagine possible plays by both sides, the best responses to those plays, the best responses to those responses, and so on. This is called reading ahead, or just reading, and it is a skill that grows with experience. Many players study books of life and death problems to increase their skill at reading more and more complicated positions.
In general, go players refer to analysis of positions as reading. One major purpose of reading is to be sure that a local position can be neglected for a while. For instance, a player may be able to make gains by playing for a certain patch of territory. Yet, this play may be worth only a few points, and thus deemed unnecessary, depending on the state of the game. With confidence in one's reading, it becomes much easier to set priorities and switch around the board. Inability to change gears at the correct time can lead to a drastic loss of opportunity. In other cases, however, switching gears at an incorrect time can lead the opponent to thinking you have read something which he has not. This may be considered a bluff.
[edit] High and low
In order to build a harmonious position, usually in the opening, one does not place all stones on the third line, nor all stones on the fourth line. "Harmonious" is here not just an aesthetic quality; rather it stands for a better level of overall (strategic) connection of the stones.
[edit] Thickness and lightness
An outwardly-facing position that cannot be attacked, that is, one which can easily get two eyes so does not need to answer enemy moves close by, is called thick. Thick positions are important as they radiate influence across the board. An error that is often made by weaker players is to make territory in front of their thick position; this is inefficient because the player is likely to get that territory anyway. Thickness is better used from a distance, as support for other actions. For example, if Black has a thick group and a weak group nearby, and White attacks the weak group, Black can have its weak group run towards its thick group. If successful, the strength of the thick group will protect the weak group. Or, if White tries to invade near a thick group, Black can try to push White towards its thick group. If Black is successful, the strength of the thick group will help destroy the invasion. A thick group can also support invasion of enemy spheres of influence.
A light group is also one that is hard to attack, but for a different reason. If a group has a large number of options, often including the sacrifice of part of it, it is called light. Because it is usually impossible to take away all or almost all options, attacking such a group is very hard for the opponent and brings little advantage. A weak group which cannot be sacrificed at will is called heavy.
[edit] Attack and defense
A large part of the middle game of a game of Go is usually spent by one player attacking the other player's weak group(s). What is important to remember is that in most cases the goal of an attack is not to kill the attacked group, but to gain territory or influence. The attack is more or less used to restrict the opponent's options and make it impossible for him to make territory or influence himself.
[edit] Territory and influence
See Go concepts
[edit] Ko fighting
Suppose that Black begins a ko by taking a stone of White's. White cannot immediately recapture; the rules state that he must, for the moment, play elsewhere. White may believe that good strategy requires he eventually recapture, but Black, on her next turn, will have the option of ending the ko, for example by filling in the spot White would use to recapture. To prevent Black from doing this, White can play a ko threat.
A ko threat is a move that forces one's opponent to respond, or risk a punishing blow. A ko threat by White will force Black to choose between responding to the threat, and allowing White to recapture (thereby continuing the ko), or ending the ko, but having a damaged, poor position elsewhere on the board.
Good ko threats, generally speaking, are ones which threaten to do so much damage to one's opponent that they must be responded to.
[edit] Sente, Gote, and Tenuki
'Sente', 'gote', and 'tenuki' are Japanese terms in Go theory. Sente loosely corresponds to taking initiative through a sequence, and gote loosely corresponds to the responsibility of defense. A Tenuki play breaks sequence, moving elsewhere. Tenuki indicates either a natural pause in sequence or a disagreement as to the importance of an area of the board. Because the Go board is so spacious, this sense of balance between attack and defense, amongst different areas, holds great importance. 'Taking gote unnecessarily' means that one defended for oneself a smaller area of the board than one could have threatened to take from the opponent, elsewhere, 'in sente'.
[edit] Go opening theory
The whole board opening is called Fuseki. The first moves are usually played on or near the 4-4 star points in the corners, because in those places it is easiest to make territory. (In order to be totally secure alone, a corner stone must be placed on the 3-3 point. However, if a stone is placed at a 4-4 point and the opponent invades, the first player can build a surrounding wall as the second (invader) is forming a live group, thus exerting strong influence on a large area.) After that, standard sequences (Joseki) are used to divide corners, and extensions along the side are made. Usually, the center area is kept empty the longest. Plays are usually on the third or fourth line—the second makes too little territory, while the fifth is too easily undermined by a play on the third. A play on the fourth line is directed more towards influence to the center, a play on the third line more towards making territory along the side.
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| Double-4 fuseki (Black) and a common Hoshi joseki in the North-West corner |
[edit] Endgame (yose)
In the endgame, if the game is close, moves that are small are still worth some points, some more than others. One must choose which of these moves is more urgent to play based not only on the points it may gain, but on whether that move is sente. Yose refers to a specific kind of play during the endgame, which yields a reduction for one's opponent. Generally, in the endgame, all the territory is staked out—there is no more to be gained. However, there are still points to be made, as well as possible ways of reducing small amounts of your opponents territory. A simple example would be a move that is dame (neutral point for you), but when filled in, it is sente, requiring white to fill a stone in his territory to answer. It would be thus said this is 'a one point reduction, with sente.'
To continue, see Go concepts.
[edit] Direction of Play
In higher levels of play, some players will say that the stones "talk" to them. It is in the nature of the stones to easily expand in certain directions. This is to say that the stones themselves state the Direction of Play that the game should continue in. The ability to recognize the correct direction of play can come from extensive play or from studying. Around AGA 5kyu, it becomes an important factor in all games. To ignore Direction of Play generally creates awkward and slow play. Understanding this concept can easily improve your game by 2 ranks. The direction of play is dictated by both the shape of the stones from both sides and the absolute position of the shape on the board. It only occasionally repeats outside of joseki.
[edit] External links
- Sensei's Library, a collaborative wiki about Go strategy and concepts
