A chess opening is the group of initial moves of a chess game. Recognized sequences of initial moves are referred to as openings by White, or defenses by Black, but opening is also used as the general term. There are many dozens of different openings, and hundreds of named variants. The Oxford Companion to Chess lists 1,327 named openings and variants. These vary widely in character from quiet positional play to wild tactical play. In addition to referring to specific move sequences, the opening is the first phase of a chess game, the other phases being the middlegame and the endgame.
A sequence of opening moves that is considered standard 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.
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, a powerful weapon in top-class competition.
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 driven to an inferior square by …d4. (Note that after 1.Nf3 the analogous 1…e5? 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: Larsen’s Opening 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 such as 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 one less tempo. 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.
A simple descriptive categorization of the chess opening is King’s Pawn Openings, Queen’s Pawn Openings, and Others.
- Double King Pawn, Symmetric or Open Games (1.e4 e5)
- Single King Pawn or Semi-Open Games (1.e4 other)
- Double Queen Pawn or Closed Games (1.d4 d5)
- Single Queen Pawn or Semi-Closed Games (1.d4 other)
- Flank openings (including 1.c4, 1.Nf3, 1.f4, and others)
- Unusual first moves for White
The open game (e4, e5) is this post’s focus.
White starts by playing 1.e4 (moving his king 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.