[edit]Popular continuations

The Black responses which are given one or more chapters in the Encyclopedia of Chess Openings (ECO) are given below, ranked in order of popularity according to ChessBase.

• 1... c5, the Sicilian Defence, is in modern practice the most common continuation. The Sicilian Defence allows Black to fight for the center by preparing to meet a d2–d4 advance with ...c5xd4. The Sicilian is among the sharpest and most analyzed openings in chess, and it has eighty chapters, B20–B99, set aside for it in ECO.
• 1... e5 leads to the classical Open Games, which includes openings like the Ruy Lopez, King's Gambit, Italian Game, Scotch Game andPetroff Defense. Also in this opening, Black is ready to meet a d2–d4 advance with e5xd4. These openings are covered in chapters C20–C99 in ECO.
• 1... e6 is the French Defence, covered in chapters C00–C19 in ECO. Black's restrained response allows White to play 2.d4. This gives White a spatial advantage, with two pawns in the center to Black's one. One or the other player will usually resolve the center tension, either by Black playing ...dxe4 or White advancing with e5. In the latter case, Black typically works to undermine White's pawn center with ...c5 and/or ...f6.
• 1... c6 is the Caro-Kann Defence, covered in chapters B10–B19 in ECO. Like the French, this is also considered to be a solid reply, but Black will often need to surrender control over the center (e.g., after 2.d4 d5 3.Nc3 Black usually plays 3...dxe4). On the other hand, the light-squared bishop will usually not wind up trapped behind its own pawns, as is common in the French.
• 1... d6 is the Pirc Defence, a hypermodern defense in which Black allows White to construct a dominant center, with the intention of subverting it later.
• 1... g6 usually leads to related openings called the Pirc Defense (1.e4 d6 2.d4 Nf6 3.Nc3 g6) and Modern Defense, respectively. These openings allow White to build up a pawn center with 2.d4, but Black will develop the king's bishop to g7 and strike back at the center. These openings are covered in chapters B06–B09 in ECO.
• 1... Nf6 is the Alekhine Defense, which invites White to attack the knight with 2.e5. Black is often forced to spend time moving the knight several times as it is chased around the board, all the while allowing White to build up a broad pawn center. Black counts on the pawns becoming overextended so that he can later undermine them. The Alekhine is covered in chapters B02–B05 of ECO.
• 1... d5, the Scandinavian Defense or Center Counter Defense, is a direct strike at the pawn at e4, forcing the situation in the center. After 2.exd5 Qxd5 3.Nc3, however, White gains time by attacking Black's prematurely developed queen. Alternatively, Black can play 2...Nf6 (theMarshall Gambit), when White chooses between 3.d4 Nxd5 4.c4 with a spatial advantage, or 3.c4, when Black usually offers a gambit with either 3...c6 or 3...e6. The Scandinavian is covered in chapter B01 in ECO.

[edit]Uncommon continuations

Apart from these eight responses, all other replies from Black are covered together in ECO chapter B00 ("Uncommon King's Pawn Opening"). A few of these are not entirely obscure, and have received extensive analysis.

• 1... Nc6 is the Nimzowitsch Defence. After 2.d4, there are two distinctive main lines: 2...e5, favored by British grandmaster Tony Miles, and 2...d5, introduced and often played by the influential Latvian-Danish player and writer Aron Nimzowitsch (1886–1935).
• 1... b6 is Owen's Defense, preparing to develop Black's bishop to b7 to put pressure on White's center.
• 1... a6 is the St. George Defence. Black prepares to advance on the queenside with 2...b5, but allows White to occupy the center with 2.d4. The opening gained some attention after Miles used it to defeat Anatoly Karpov in 1980.^[2]
• 1... g5 is the Borg Defence ("Grob" backwards) or Basman Defence, often played by IM Michael Basman. The move weakens the kingsideseverely, but according to Modern Chess Openings (MCO), Black is only somewhat worse.^[3]

[edit]Rare continuations

The remaining replies to 1.e4 are very rare, and have not received significant and serious attention by masters. MCO does not cover them, considering them so bad to not merit discussion.^[4] These openings sometimes lead to wild and exciting games, and are occasionally employed by weaker players to get better trained opponents "out-of-book". Some have exotic names, they are listed below along with instances where they have been used by strong players.