In chess the word "opening" has two common meanings, both of which are discussed in this article. Chessplayers are so familiar with these two meanings that many books and articles never state the distinction and may switch without notice from one meaning to the other.
The earliest stage of a game is known as the opening. For several moves players are mainly concerned with transferring their pieces from their starting positions to somewhere more useful.
A chess opening is the group of initial moves of a chess game (the opening moves in the previous sense). Recognized sequences of opening moves are referred to as openings as initiated by White or defenses, as created in reply by Black. There are many dozens of different openings, and hundreds of named variants. The Oxford Companion to Chess lists 1327 named openings and variants. These vary widely in character from quiet positional play (e.g. the Réti Opening and some lines of the Queen's Gambit Declined) to wild tactical play (e.g. the Latvian Gambit and Two Knights Defense, particularly the Traxler Variation).
A sequence of opening moves that is considered standard (often cataloged in a reference work such as the Encyclopedia of Chess Openings) is referred to as "the book moves", or simply "book". These reference works often present these move sequences in simple algebraic notation, opening trees, or theory tables. When a game begins to deviate from known opening theory, the players are said to be "out of book". In some opening lines, the moves considered best for both sides have been worked out for twenty to twenty-five moves or more. Professional chessplayers spend years studying openings, and continue doing so throughout their careers, as opening theory continues to evolve.
A new sequence of moves in the opening is referred to as a "theoretical novelty". When kept secret until used in a competitive game it is often known as a "prepared variation", and can be a formidable weapon in top-class competition.
For a list of openings as classified by the Encyclopedia of Chess Openings, see List of chess openings.
Since about the 1950s another objective has gradually become more dominant. According to IM Jeremy Silman, the purpose of the opening is to create dynamic imbalances between the two sides, which will determine the character of the middlegame and the strategic plans chosen by both sides. For example, in the Winawer Variation of the French, White will try to use his bishop pair and space advantage to mount an attack on Black's kingside, while Black will seek simplifying exchanges (in particular, trading off one of White's bishops to blunt this advantage) and counterattack against the weakened pawns on White's queenside; both players accept different combinations of advantages and disadvantages. This idea was a doctrine of the Soviet school of chess, which has dominated the game since about 1945.
A third objective, which is complementary to the previous ones and has been common since the 19th century, is to lure the opponent into types of position with which the player is more familiar and comfortable than the opponent. This is usually done by transpositions, in which a game that apparently starts with one opening can reach a position that is normally produced by a different opening.
Apart from these ideas, other strategies used in the middlegame may also be carried out in the opening. These include preparing pawn breaks to create counterplay, creating weaknesses in the opponent's pawn structure, seizing control of key squares, making favourable exchanges of minor pieces (e.g. gaining the bishop pair), or gaining a space advantage, whether in the centre or on the flanks.
The oldest openings tend to be named for geographic places and people. Many openings are named after nationalities, for example Indian, English, Spanish, French, Dutch, Scotch, Russian, Italian, Scandinavian, and Sicilian. Cities are also used, such as Vienna, Berlin, and Wilkes-Barre. The Catalan System is named after the Catalonia region of Spain.
Chess players' names are the most common sources of opening names. The name given to an opening is not always that of the first player to adopt it; often an opening is named for the player who was the first to popularize it or to publish analysis of it. Eponymic openings include the Ruy Lopez, Alekhine's Defense, Morphy Defense, and the Réti System. Some opening names honor two people, such as with the Caro-Kann.
A few opening names are descriptive, such as Giuoco Piano (quiet game). More prosaic descriptions include Two Knights and Four Knights. Descriptive names are less common than openings named for places and people.
Some openings have been given fanciful names, often names of animals. This practice became more common in the 20th century. By then, most of the more common and traditional sequences of opening moves had already been named, so these tend to be unusual or recently developed openings like the Orangutan, Hippopotamus, Elephant, and Hedgehog.
Many terms are used for the opening as well. In addition to Opening, common terms include Game, Defense, Gambit, and Variation; less common terms are System, Attack, Counterattack, Countergambit, Reversed, and Inverted. To make matters more confusing, these terms are used very inconsistently. Consider some of the openings named for nationalities: Scotch Game, English Opening, French Defense, and Russian Game — the Scotch Game and the English Opening are both White openings (White chooses to play), the French is indeed a defense but so is the Russian Game. Although these do not have precise definitions, here are some general observations about how they are used. Game : Used only for some of the oldest openings, for example Scotch Game, Vienna Game, and Four Knights Game. Opening : Along with Variation, this is the most common term. Variation : Usually used to describe a line within a more general opening, for example the Exchange Variation of the Queen's Gambit Declined. Defense : Always refers to an opening chosen by Black, such as Two Knights Defense or King's Indian Defense, unless, of course, it has 'reversed' in front of it, which makes it an opening for white. The term "defense" does not imply passivity; many defenses are quite aggressive (such as the Nimzo-Indian Defense). Gambit : An opening that involves the sacrifice of material, usually one or more pawns. Gambits can be played by White (e.g., King's Gambit) or Black (e.g., Latvian Gambit). The full name often includes Accepted or Declined depending on whether the opponent took the offered material, as in the Queen's Gambit Accepted and Queen's Gambit Declined. In some cases, the sacrifice of material is only temporary. The Queen's Gambit is not a true gambit because there is no good way for Black to keep the pawn . Countergambit : Any gambit played by Black; sometimes this will be in response to a White gambit. Examples of this include the Albin Countergambit to the Queen's Gambit, the Falkbeer Countergambit to the King's Gambit, and the Greco Counter Gambit (the former name of the Latvian Gambit). System : A method of development that can be used against many different setups by the opponent. Examples include Colle System, Stonewall Attack, Réti System, Barcza System, and Hedgehog System. Attack : Sometimes used to describe an aggressive or provocative variation such as the Albin-Chatard Attack (or Chatard-Alekhine Attack), the Fried Liver Attack in the Two Knights Defense, and the Grob Attack. In other cases it refers to a defensive system by Black when adopted by White, as in King's Indian Attack. In still other cases the name seems to be used ironically, as with the fairly inoffensive Durkin's Attack (also called the Durkin Opening). Reversed, Inverted : A Black opening played by White, or more rarely a White opening played by Black. Examples include Sicilian Reversed (from the English Opening), and the Inverted Hungarian.
A small minority of openings are prefixed with "Anti-". These are openings intended to avoid a particular line otherwise available to one's opponent, for example the Anti-Marshall (against the Marshall (Counter) Attack in the Ruy Lopez) and the Anti-Meran Gambit (against the Meran Variation of the Semi-Slav Defense).
The beginning chess position offers White twenty possible first moves. Of these, 1.e4, 1.d4, 1.Nf3, and 1.c4 are by far the most popular as these moves do the most to promote rapid development and control of the center. A few other opening moves are considered reasonable but less consistent with opening principles than the four most popular moves. The Dunst Opening, 1.Nc3, develops a knight to a good square, but is somewhat inflexible because it blocks White's c-pawn; also, after 1...d5 the knight is liable to be kicked to an inferior square by ...d4. (Note that after 1.Nf3 the analogous 1...e5? just loses a pawn.) Bird's Opening, 1.f4, addresses center control but not development and weakens the king position slightly. The Sokolsky Opening 1.b4 and the King's and Queen's fianchettos 1.b3 and 1.g3 aid development a bit, but they only address center control peripherally and are slower than the more popular openings. The eleven remaining possibilities are rarely played at the top levels of chess. Of these, the best are merely slow such as 1.c3, 1.d3, and 1.e3. Worse possibilities either ignore the center and development like 1.a3, weaken White's position (for instance, 1.f3 and 1.g4), or place the knights on poor squares (1.Na3 and 1.Nh3).
Black has twenty possible responses to White's opening move. Many of these are mirror images of the most popular first moves for White, but with a tempo less. Defenses beginning with 1...c6 and 1...e6, often followed by the center thrust 2...d5, are also popular. Defenses with an early ...d6 coupled with a kingside fianchetto are also commonly played.
The most important scheme of classifying chess openings for serious players is by ECO code, a series of 500 opening codes assigned by the Encyclopaedia of Chess Openings. Although these codes are invaluable for the serious study of the chess opening, they are not very practical for a broad survey of the chess opening as the codes obscure common structural features between related openings.
A simple descriptive categorization of the chess opening is King's Pawn Openings, Queen's Pawn Openings, and Others. Since these categories are still individually very large, it is common to divide each of them further. One reasonable way to group the openings is
The Indian systems (1.d4 Nf6) are the most important of the Semi-Closed Games, and warrant separate treatment.
White starts by playing 1.e4 (moving his King's pawn two spaces). This is the most popular opening move and it has many strengths — it immediately works on controlling the center, and it frees two pieces (the queen and a bishop). The oldest openings in chess follow 1.e4. Bobby Fischer rated 1.e4 as "best by test". On the downside, 1.e4 places a pawn on an undefended square and weakens d4 and f4; the Hungarian master Gyula Breyer melodramatically declared that "After 1.e4 White's game is in its last throes". If Black mirrors White's move and replies with 1...e5, the result is an open game.
The most popular second move for White is 2.Nf3 attacking Black's king pawn, preparing for a kingside castle, and anticipating the advance of the queen pawn to d4. Black's most common reply is 2...Nc6, which usually leads to the Ruy Lopez (3.Bb5), Scotch Game (3.d4), or Italian Game (3.Bc4). If Black instead maintains symmetry and counterattacks White's center with 2...Nf6 then the Petrov's Defense results. The Philidor Defense (2...d6) is not popular in modern chess because it allows White an easy space advantage while Black's position remains cramped and passive, although solid. Other responses to 2.Nf3 are not seen in master play.
The most popular alternatives to 2.Nf3 are the Vienna Game (2.Nc3), the Bishop's Opening (2.Bc4), and the King's Gambit (2.f4). These openings have some similarities with each other, in particular the Bishop's Opening frequently transposes to variations of the Vienna Game. The King's Gambit was extremely popular in the 19th century. White sacrifices a pawn for quick development and to pull a black pawn out of the center. The Vienna Game also frequently features attacks on the Black center by means of a f2-f4 pawn advance.
In the Center Game (2.d4) White immediately opens the center but if the pawn is to be recovered after 2...exd4, White must contend with a slightly premature queen development after 3.Qxd4. An alternative is to sacrifice one or two pawns, for example in the Danish Gambit.
Many other variations after 1.e4 e5 have been studied; see Open Game for details.
The Sicilian and French Defenses lead to unbalanced positions that can offer exciting play with both sides having chances to win. The Caro-Kann Defense is solid as Black intends to use his c-pawn to support his center (1.e4 c6 2.d4 d5). Alekhine's, the Pirc and the Modern are hypermodern openings in which Black tempts White to build a large center with the goal of attacking it with pieces.
Other semi-open games have been studied but are less common; see Semi-Open Game for details.
The most important closed openings are in the Queen's Gambit family (White plays 2.c4). The Queen's Gambit is somewhat misnamed, since White can always regain the offered pawn if desired. In the Queen's Gambit Accepted, Black plays ...dxc4, giving up the center for free development and the chance to try to give White an isolated queen pawn with a subsequent ...c5 and ...cxd5. White will get active pieces and possibilities for the attack. Black has two popular ways to decline the pawn, the Slav (2...c6) and the Queen's Gambit Declined (2...e6). Both of these moves lead to an immense forest of variations that can require a great deal of opening study to play well. Among the many possibilities in the Queen's Gambit Declined are the Orthodox Defense, Lasker's Defense, the Cambridge Springs Defense, the Tartakower Variation, and the Tarrasch and Semi-Tarrasch Defenses. Black replies to the Queen's Gambit other than 2...dxc4, 2...c6, and 2...e6 are uncommon.
The Colle System and Stonewall Attack are classified as Queen's Pawn Games because White plays d4 but not c4. They are also examples of Systems, rather than specific opening variations. White develops aiming for a particular formation without great concern over how Black chooses to defend. Both systems are popular with club players because they are easy to learn, but are rarely used by professionals because a well prepared opponent playing Black can equalize fairly easily. The Stonewall is characterized by the White pawn formation on c3, d4, e3, and f4, and can be achieved by several move orders and against many different Black setups. The position in the diagram and the move sequence given below are typical.
Other closed openings have been studied but are less common; see Closed Game for details.
Advocated by Nimzowitsch as early as 1913, the Nimzo-Indian Defense was the first of the Indian systems to gain full acceptance. It remains one of the most popular and well-respected defenses to 1.d4 and White often adopts move orders designed to avoid it. Black attacks the center with pieces and is prepared to trade a bishop for a knight to weaken White's queenside with doubled pawns.
The King's Indian Defense is aggressive and somewhat risky, and generally indicates that Black will not be satisfied with a draw. Although it was played occasionally as early as the late 19th century, the King's Indian was considered inferior until the 1940s when it was featured in the games of Bronstein, Boleslavsky, and Reshevsky. Fischer's favored defense to 1.d4, its popularity faded in the mid-1970s. Kasparov's successes with the defense restored the King's Indian to prominence in the 1980s.
Ernst Grünfeld debuted the Grünfeld Defense in 1922. Distinguished by the move 3...d5, Grünfeld intended it as an improvement to the King's Indian which was not considered entirely satisfactory at that time. The Grünfeld has been adopted by World Champions Smyslov, Fischer, and Kasparov.
The Queen's Indian Defense is considered solid, safe, and perhaps somewhat drawish. Black often chooses the Queen's Indian when White avoids the Nimzo-Indian by playing 3.Nf3 instead of 3.Nc3. Black constructs a sound position that makes no positional concessions, although sometimes it is difficult for Black to obtain good winning chances. Karpov is a leading expert in this opening.
The Modern Benoni Defense is a risky attempt by Black to unbalance the position and gain active piece play at the cost of allowing White a pawn wedge at d5 and a central majority. Tal popularized the defense in the 1960s by winning several brilliant games with it, and Bobby Fischer occasionally adopted it, with good results, including a win in his 1972 world championship match against Boris Spassky. Often Black adopts a slightly different move order, playing 2...e6 before 3...c5 in order to avoid the sharpest lines for White.
The Benko Gambit is often played by strong players, and is very popular at lower levels. Black plays to open lines on the queenside where White will be subject to considerable pressure. If White accepts the gambit, Black's compensation is positional rather than tactical, and his initiative can last even after many piece exchanges and well into the endgame. White often chooses instead either to decline the gambit pawn or return it.
The Catalan Opening is characterized by White forming a pawn center at d4 and c4 and fianchettoing his king's bishop. It resembles a combination of the Queen's Gambit and Réti Opening. Since the Catalan can be reached from many different move orders, (one Queen's Gambit Declined-like move sequence is 1.d4 d5 2.c4 e6 3.Nf3 Nf6 4.g3), it is sometimes called the Catalan System.
The most important Indian Defenses are listed below, but many others have been studied and played; see Indian Defense for details.
Several other uncommon semi-closed openings have been named and studied, see Semi-Closed Game for details.
If White opens with 1.Nf3, the game often becomes one of the d4 openings (closed games or semi-closed games) by a different move order (this is called transposition), but unique openings such as the Réti and King's Indian Attack are also common. The Réti itself is characterized by White playing 1.Nf3, fianchettoing one or both bishops, and not playing an early d4 (which would generally transpose into one of the 1.d4 openings).
The King's Indian Attack (KIA) is a system of development that White may use in reply to almost any Black opening moves. The characteristic KIA setup is 1.Nf3, 2.g3, 3.Bg2, 4.0-0, 5.d3, 6.Nbd2, and 7.e4, although these moves may be played in many different orders. In fact, the KIA is probably most often reached after 1.e4 when White uses it to respond to a Black attempt to play one of the Semi-open games such as the Caro-Kann, French, or Sicilian, or even the open games which usually come after 1.e4 e5. Its greatest appeal may be that by adopting a set pattern of development, White can avoid the large amount of opening study required to prepare to meet the many different possible Black replies to 1.e4.
The English Opening (1.c4) also frequently transposes into a d4 opening, but it can take on independent character as well including symmetrical variations (1.c4 c5) and the Sicilian Defense in reverse (1.c4 e5).
Larsen's Opening (1.b3) and the Sokolsky Opening (1.b4) are occasionally seen in grandmaster play. Benko used 1.g3 to defeat both Fischer and Tal in the 1962 Candidates Tournament in Curaçao.
With Bird's Opening (1.f4) White tries to get a strong grip on the e5-square. The opening can resemble a Dutch Defense in reverse after 1.f4 d5, or Black may try to disrupt White by playing 1...e5!? (From's Gambit).