chess opening

This article uses algebraic notation to describe chess moves.

A chess opening is the group of initial moves of a chess game (the opening moves). 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.^[1] 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. A new move in the opening is referred to as a "theoretical novelty". 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.

For a list of openings as classified by the Encyclopedia of Chess Openings, see List of chess openings.

Starting position

FEN

Aims of the opening

Although a wide variety of moves can be played in the opening, the aims behind them are, broadly speaking, the same. First and foremost, the aim is to avoid being checkmated and avoid losing material, as in other phases of the game. However, assuming neither player makes a blunder in the opening, the main aims include:

Development: One of the main aims of the opening is to mobilize the pieces on useful squares where they will have impact on the game. To this end, knights are usually developed to f3, c3, f6 and c6 (or sometimes e2, d2, e7 or d7), and both player's e- and d-pawns are moved so the bishops can be developed (alternatively, the bishops may be fianchettoed with a maneuver such as g3 and Bg2). Rapid mobilization is the key. The queen, however, is not usually played to a central position until later in the game, as it is liable to be attacked otherwise, when its value means it has to be moved, which can waste time.
Control of the center: At the start of the game, it is not clear on which part of the board the pieces will be needed. However, control of the central squares allows pieces to be moved to any part of the board relatively easily, and can also have a cramping effect on the opponent. The classical view is that central control is best effected by placing pawns there, ideally establishing pawns on d4 and e4 (or d5 and e5 for Black). However, the hypermodern school showed that it was not always necessary or even desirable to occupy the center in this way, and that too broad a pawn front could be attacked and destroyed, leaving its architect vulnerable; an impressive looking pawn center is worth little unless it can be maintained. The hypermoderns instead advocated controlling the center from a distance with pieces, breaking down one's opponent center, and only taking over the center oneself later in the game. This leads to openings such as the Alekhine Defense - in a line like 1. e4 Nf6 2. e5 Nd5 3. d4 d6 4. c4 Nb6 5. f4 (the Four Pawns Attack), White has a formidable pawn center for the moment, but Black hopes to undermine it later in the game, leaving White's position exposed.
King safety: The king is somewhat exposed in the middle of the board. Measures must be taken to reduce his vulnerability. It is therefore common for both players to either castle in the opening (simultaneously developing one of the rooks) or to otherwise bring the king to the side of the board via artificial castling.
Avoid pawn weaknesses: Most openings strive to avoid the creation of pawn weaknesses such as isolated, doubled and backward pawns, pawn islands, etc. Some openings sacrifice endgame considerations for a quick attack on the opponent's position. Some unbalanced openings for black, in particular, make use of this idea; such as the Dutch, and the Sicilian. While other openings, such as the Alekhine and the Benoni invite the opponent to overextend and form pawn weaknesses. Certain openings accept pawn weaknesses in exchange for compensation in the form of dynamic play. (See pawn structure.)
Piece coordination: As each player mobilizes his or her pieces, each attempts to assure that they are working harmoniously towards the control of key squares.

Apart from these ideas, other strategic plans 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.

In more general terms, many writers (for example, Reuben Fine in The Ideas Behind the Chess Openings) have commented that it is White's task in the opening to preserve and increase the advantage conferred by moving first, while Black's task is to equalize the game. Many openings, however, give Black a chance to play aggressively for advantage from the very start.

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.^[2] 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.

Opening nomenclature

Major changes in the rules of chess in the late fifteenth century increased the speed of the game, consequently emphasizing the importance of opening study. Thus, early chess books, such as the 1497 text of Luis Ramirez de Lucena presents opening analysis, as does Pedro Damiano (1512), and Ruy López de Segura (1561). Ruy Lopez's disagreement with Damiano regarding the merits of 2...Nc6 led to 3.Bb5 (after 1.e4 e5 2.Nf3 Nc6) being named for him as the Ruy Lopez or Spanish Opening.^[3] Opening theory was studied more scientifically from the 1840s on, and many opening variations were discovered and named in this period and later. Opening nomenclature developed haphazardly, and most names are historical accidents not based on systematic principles.

The oldest openings tend to be named for geographic places and people. Many openings are named after nationalities, for example 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 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 (Italian: "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 don't 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 Defence).
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. For example, after 1.d4 d5 2.c4 dxc4 (the Queen's Gambit Accepted), White can regain the pawn immediately by 3.Qa4+ if he wishes.
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).

Classification of chess openings

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 king-side 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