Go opening theory

In the game of Go, the term opening theory (also opening game or early game —borrowed from Chess terminology) refers to concepts which underlie where, why, in what order, and in what shapes the first several moves are played. The "middle game" typically begins once the basic foundational areas (called moyo) are established and "fighting" begins—when moves directly attack an opponent's stone groups.

The opening is conceptually divided into the study of sequences that are whole board openings (fuseki) and those that are corner openings (joseki), where each is a series of played moves for both black and white which have been studied for their balance (with the other) and for any weaknesses to various strong countermoves. Because moves in the fuseki are almost always also part of a joseki sequence, joseki and fuseki are only regarded as "sequences" inasmuch as certain plays are regarded as sente, or forced plays which require specific responses (moves within joseki and fuseki may differ in terms of sente).

As played on a large board (ie. a 19x19 line goban), the basic concept for the opening is simply,

plays in the corners are more efficient for making territory than plays on the sides or in the center.

History

Go openings have been studied in depth for many centuries, and center upon concepts of finding balance with the opponent. Because black moves first, opening moves for black are based on the concept of exploiting that first-move advantage (along with sente) to gain influence (or strength) and thus establish areas of territory. There is no complete theory of go, simply because the number of possible variations makes any literal study impossible. Hence even the opening is subject to changes of fashion, and also some notable periods of innovation.

Certain professional players are known for their use of specific or innovative types of openings, and their ability to combine their use of those openings with other strengths in competitive play.

The 10-10 point

Perhaps the most highly regarded player of the 20th century, Go Seigen, created an uproar when he played his third move (Black 5) on tengen, in a 1933 game against Honinbo Shusai, the top player of the time.

Considered an unwise move in a normal context, it was considered an insult against someone of Honinbo's stature. Seigen lost the controversial 4-month game, which was played over 14 sessions in a ryokan in Tokyo from 16 October 1933 to 19 January 1934. There was a persistent rumour that Seigen had received help from Maeda Nobuaki, one of Honinbo's students.

Concepts

Opening theory is less dominant in terms of study, for those wanting to reach a good amateur level, than in chess or shogi. It is, however, an important component of Go knowledge; though there is no single, codified source for it.

The standard sequences for the joseki (corner plays) in many cases come to a definite end, after which both players should move elsewhere. In some cases a sharp local struggle breaks out, which neither player should neglect. For those cases, the result of the opening may develop out of a 10×10 corner area into the rest of the board. Analysis without taking into account what other stones are in place then becomes somewhat meaningless. The longest 'book' corner openings are about 50-ply.

Most corner openings do not have special or picturesque names. A few that do are known by Japanese names: the taisha, the nadare (avalanche), the Magic sword of Muramasa. These are amongst the most complex, and are contraindicated for novices.

Whole-board openings

Because each move is typically isolated and unforced (ie. not a sente move) patterns for play on the whole board have seen much less systematic study than for joseki, which are often contact moves which require specific and immediate responses.Hence a game of Go may easily explore an unfamiliar path.

Only a relatively small proportion of openings have a recognised name. These include the Three stars opening (sanrensei), Two stars opening (nirensei), and Chinese opening (Chinese fuseki). To be more precise, these are names for the moyo formations which Black makes on one side of the board. Since White has a choice of perhaps two dozen legitimate variations on the other side, these are in fact large complexes of openings.

The Chinese opening, which has an intricate history but was indeed developed by Chinese players, was very popular from about 1970 onwards, and has by go standards a thoroughly-researched theory.

Joseki

Joseki are "sequences" of moves which have been

played and documented in high-level play, and
studied and deemed as consisting of optimal (balanced) moves for both sides.

Joseki is a Japanese word (定石) (Korean jungsuk), where jo (定) means "fixed" or "set", and seki (石) means stone(s). It thus literally means "set stones", as in "set pattern". Variations are shown to lead to different positional advantages and disadvantages for the two players in certain overall game situations. "Balance" typically refers to an equitable trade-off between securing territory in the corner versus making good thickness toward the sides and center.

In application these concepts are in fact very dynamic, and often joseki are deviated from depending on the needs of the situation, and the opportunities available. While learning joseki is a tool to defend against a local loss, players always seek to take advantage of weaknesses in the opponent's shapes, often deviating from the joseki.

Usually josekis happen in corners in the opening stage. However, there are also josekis for "middle game".

The current body of joseki are not fixed, but patterns that have gained acceptance in professional games. That is, they form a consensus judgement that might change in the future, or with certain caveats. Hence the basic definition may be misleading for new players in that joseki can be misconstrued as foolproof and unalterable, and are otherwise optimal for all situations. Many joseki are in fact useful only for study within an artificially confined corner, and in real play are only considered good form when used in proper combination with other plays on the board (ie. other joseki and fuseki moves). Knowing a particular joseki simply means that one knows a sequence of moves, resulting in a balance or fair trade-off between their positions. This is in practice much easier than appraising how joseki relate to the rest of the board —hence knowledge of joseki is regarded as shallow, when compared with the ability to integrate a strategy into a complex game landscape.

There is a go proverb that states that "learning joseki loses two stones in strength," meaning that rote learning of sequences is not advantageous. Rather learning from joseki should be a player's goal. Hence the study of joseki is regarded as a double-edged sword and useful only if learned not by rote but rather by understanding the principles behind each move. Every joseki should be used as a specific tool that leaves the board in a particular shape. Just as using an improper tool in machinery can be devastating, choosing the wrong joseki can easily be worse than improvising one's own moves. In his book A Way of Play for the 21st Century Go Seigen compared choosing the proper joseki to choosing the proper medicine —pick the right one, and you feel better. Pick the wrong one and you die.(par.) Rui Naiwei similarly remarked that playing joseki is easy choosing the right one [in a game is hard.(par.)

A joseki may fall out of use for various reasons, some of which may often seem minor to the amateur player, and professionals may consider one variation suboptimal for a very specific reason —one which strong amateurs are not likely to exploit. There is no definitive guide to what is joseki; the situation with joseki dictionaries is similar to that of natural language dictionaries, in that some entries are obsolete and the listing is not likely to be complete.

While some claim that studying joseki is an important part of developing one's strength as a player, more regard the study of Life and death to be more important.

External links

Kogo's Joseki Dictionary
- Extensive repository of the most common joseki, stored in the smart go format.
Opening article at Sensei's library
- This is the introductory opening article at the Go wiki "Sensei's Library".
  It branches out into several sub-articles and covers most of the basic opening patterns.
Go Learn - openings
- Series of articles on openings written by Charles Matthews 3-dan.