Gomoku strategy and tactics

In Go, tactics deal with immediate fighting between stones, capturing and saving stones, life, death and other issues localized to a specific part of the board. Larger issues, not limited to only part of the board, are referred to as strategy, and are covered in their own section


Capturing tactics

There are several tactical constructs aimed at capturing stones. These are among the first things a player learns after understanding the rules. Recognizing the possibility that stones can be captured using these techniques is an important step forward.



A ladder. Black cannot escape unless the ladder connects to friendly stones further down the board.
The most basic technique is the ladder. To capture stones in a ladder, a player uses a constant series of capture threats—called atari—to force the opponent into a zigzag pattern as shown in the diagram to the right. Unless the pattern runs into friendly stones along the way, the stones in the ladder cannot avoid capture. Experienced players will recognize the futility of continuing the pattern and will play elsewhere. The presence of a ladder on the board does give a player the option to play a stone in the path of the ladder, thereby threatening to rescue their stones, forcing a response. Such a move is called a ladder breaker and may be a powerful strategic move. In the diagram, Black has the option of playing a ladder breaker.




Another technique to capture stones is the so-called net, also known by its Japanese name, geta. This refers to a move that loosely surrounds some stones, preventing their escape in all directions. An example is given in the diagram to the left. It is generally better to capture stones in a net than in a ladder, because a net does not depend on the condition that there are no opposing stones in the way, nor does it allow the opponent to play a strategic ladder breaker





A third technique to capture stones is the snapback. In a snapback, one player allows a single stone to be captured, then immediately plays on the point formerly occupied by that stone; by so doing, the player captures a larger group of their opponent's stones, in effect snapping back at those stones. An example can be seen on the right. As with the ladder, an experienced player will not play out such a sequence, recognizing the futility of capturing only to be captured back immediately.

Reading ahead
One of the most important skills required for strong tactical play is the ability to read ahead. Reading ahead includes considering available moves to play, the possible responses to each move, and the subsequent possibilities after each of those responses. Some of the strongest players of the game can read up to 40 moves ahead even in complicated positions.

As explained in the scoring rules, some stone formations can never be captured and are said to be alive, while other stones may be in the position where they cannot avoid being captured and are said to be dead. Much of the practice material available to students of the game comes in the form of life and death problems, also known as tsumego.[67] In such problems, players are challenged to find the vital move sequence that will kill a group of the opponent or save a group of their own. Tsumego are considered an excellent way to train a player's ability at reading ahead and are available for all skill levels, some posing a challenge even to top players.

Ko fighting


In situations when the Ko rule applies, a ko fight may occur. If the player who is prohibited from capture is of the opinion that the capture is important, because it prevents a large group of stones from being captured for instance, the player may play a ko threat. This is a move elsewhere on the board that threatens to make a large profit if the opponent does not respond. If the opponent does respond to the ko threat, the situation on the board has changed, and the prohibition on capturing the ko no longer applies. Thus the player who made the ko threat may now recapture the ko. Their opponent is then in the same situation and can either play a ko threat as well, or concede the ko by simply playing elsewhere. If a player concedes the ko, either because they do not think it important or because there are no moves left that could function as a ko threat, they have lost the ko, and their opponent may connect the ko.

Instead of responding to a ko threat, a player may also choose to ignore the threat and connect the ko.They thereby win the ko, but at a cost. The choice of when to respond to a threat and when to ignore it is a subtle one, which requires a player to consider many factors, including how much is gained by connecting, how much is lost by not responding, how many possible ko threats both players have remaining, what the optimal order of playing them is, and what the size—points lost or gained—of each of the remaining threats is.

Frequently, the winner of the ko fight does not connect the ko but instead captures one of the chains that constituted their opponent's side of the ko. In some cases, this leads to another ko fight at a neighboring location.

Basic concepts

Basic strategic aspects include the following:

Connection: Keeping one's own stones connected means that fewer groups need defense.
Cut: Keeping opposing stones disconnected means that the opponent needs to defend more groups.
Life: This is the ability of stones to permanently avoid capture. The simplest and usual way is for the group to surround two eyes (separate empty areas), so that filling one eye will not kill the group; as a result, any such move is suicidal and the group cannot be captured. The fundamental strategy of Go is to create groups with life while preventing one's opponent from doing the same.
Mutual life (seki): A situation in which neither player can play to a particular point without then allowing the other player to play at another point to capture. The most common example is that of adjacent groups that share two "eyes". If either player plays in one of the eyes, they reduce their own group to a single eye, allowing their opponent to capture it on the next move.
Death: The absence of life coupled with the inability to create it, resulting in the eventual removal of a group.
Invasion: Setting up a new living position inside an area where the opponent has greater influence, as a means of balancing territory.
Reduction: Placing a stone far enough into the opponent's area of influence to reduce the amount of territory they will eventually get, but not so far in that it can be cut off from friendly stones outside.
Sente: A play that forces one's opponent to respond (gote), such as placing an opponent's group in atari (immediate danger of capture). A player who can regularly play sente has the initiative, as in chess, and can control the flow of the game.
Sacrifice: Allowing a group to die in order to carry out a play, or plan, in a more important area.
The strategy involved can become very abstract and complex. High-level players spend years improving their understanding of strategy, and a novice may play many hundreds of games against opponents before being able to win regularly.

Opening strategy

In the opening of the game, players will usually play in the corners of the board first, as the presence of two edges make it easier for them to surround territory and establish their stones.[68] After the corners, focus moves to the sides, where there is still one edge to support a player's stones. Opening moves are generally on the third and fourth line from the edge, with occasional moves on the second and fifth lines. In general, stones on the third line offer stability and are good defensive moves, whereas stones on the fourth line influence more of the board and are good attacking moves.

In the opening, players often play established sequences called joseki, which are locally balanced exchanges; however, the joseki chosen should also produce a satisfactory result on a global scale. It is generally advisable to keep a balance between territory and influence. Which of these gets precedence is often a matter of individual taste.


Phases of the game


While the opening plays in a game have a distinct set of aims, they usually make up only 10% to at most 20% of the game. In other words, in a game of 250 plays, there may be around 30 or so opening plays, with limited "fighting". At the end of such a game, there will also be perhaps 100 plays that are counted as "endgame", in which territories are finished off definitively and all issues on capturing stones become clear. The middle phase of the game is the most combative, and usually lasts for more than 100 plays. During the middlegame, or just "the fighting", the players invade each others' frameworks, and attack weak groups, formations that lack the necessary two eyes for viability. Such groups must run away, i.e. expand to avoid enclosure, giving a dynamic feeling to the struggle. It is quite possible that one player will succeed in capturing a large weak group of the opponent's, which will often prove decisive and end the game by a resignation. But matters may be more complex yet, with major trade-offs, apparently dead groups reviving, and skillful play to attack in such a way as to construct territories rather than to kill.

The end of the middlegame and transition to the endgame is marked by a few features. The game breaks up into areas that do not affect each other (with a caveat about ko fights), where before the central area of the board related to all parts of it. No large weak groups are still in serious danger. Plays can reasonably be attributed some definite value, such as 20 points or fewer, rather than simply being necessary to compete. Both players set limited objectives in their plans, in making or destroying territory, capturing or saving stones. These changing aspects of the game usually occur at much the same time, for strong players. In brief, the middlegame switches into the endgame when the concepts of strategy and influence need reassessment in terms of concrete final results on the board.