English Opening

The Symmetrical Defence[6] (classified A30–39 in ECO) is 1...c5, and is so named because both of the c-pawns are advanced two squares, maintaining symmetry. Note that Black can reach the Symmetrical Defence through many move orders by deferring ...c5, and often does. For example, 1.c4 Nf6 2.Nc3 (or 2.Nf3) c5.

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Symmetrical Defence: 1.c4 c5

Either player may make an early break in the centre with the d-pawn. Similar to the Open Sicilian, an early d2–d4 for White can arise on the third move in the Symmetrical Defence with 2.Nf3, where Black has chosen one of 2...Nc6, 2...e6, 2...d6, or 2...g6.

After 3.d4, the game usually continues with 3...cxd4 4.Nxd4. The games can give a large variety of positional and tactical ideas, and can transpose into variants of the Open Sicilian involving the Maróczy Bind, such as the Accelerated Dragon, Taimanov, Kan, or Kalashnikov Variations, if White plays e4 in a later move. If Black manages to play d5 before White plays e4, then the game could transpose into variants of the Queen's Gambit Declined.

When Black plays 2...Nf6, these lines are often called the Anti-Benoni, since these positions are often reached after the transposition 1.d4 Nf6 2.c4 c5 3.Nf3, where White avoided the Benoni Defense that would arise after 3.d5. After 3...cxd4 4.Nxd4, Black could follow up with 4...e5 forcing White's knight to go to the queenside and avoiding the transpositions to the Sicilian or the QGD; however, White could avoid the line by first playing 3.Nc3 and then play 4.d4, if Black doesn't play 3...d5 (see below). Same as above, the position could transpose into a Queen's Gambit Declined or an Open Sicilian involving the Maróczy Bind.

• With 2.e3 Nf6, the position transposes into a Panov–Botvinnik Attack after 3.d4 cxd4 4.exd4 d5. Alternatively, the position could transpose into a Tarrasch Defense in the Queen's Gambit Declined.
• A typical line of play where Black plays an early ...d5 is 1.c4 c5 2.Nc3 Nf6 3.Nf3 d5, when White usually trades off in the centre 4.cxd5 Nxd5. White can either challenge the centre with 5.d4 or 5.e4 or allow Black a space advantage in the centre with 5.g3. In the latter case, Black can play 5...Nc6 6.Bg2 Nc7 followed by 7...e5, reaching a reversed Maróczy Bind position called the Rubinstein System.

There are several types of positions that can arise from the Symmetrical Defence. Among the ideas are:[7]

• The Hedgehog system[8] involves a solid but flexible defence in which Black develops by b6, e6, Bb7, and Be7, before controlling the fifth rank with moves such as a6 and d6. The game typically involves extended maneuvering, but both players need to be on the lookout for favourable pawn advances and pawn breaks.
• The double fianchetto defence involves Black developing both bishops by fianchetto to g7 and b7. The line is fairly solid and difficult to defeat at the grandmaster level. Some lines are considered highly drawish, for instance if White's bishops are also fianchettoed to g2 and b2 there may be many piece exchanges leading to a simplified and equal position.

The Reversed Sicilian (classified A20–29 in ECO) is another broad category of defence, introduced by the response 1...e5. Note again, that Black can delay playing ...e5, for example 1.c4 Nf6 2.Nc3 Nc6 3.Nf3 e5 whereupon even though ...e5 has been delayed, once it is played the defence is classified as a Reversed Sicilian.

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Reversed Sicilian: 1...e5

After 1...e5, White has Black's position in the Sicilian but with an extra tempo. This is often called the Reversed Sicilian,[9] though others call it the King's English.[10] Bruce Leverett, writing the English chapter in MCO-14, stated, "It is natural to treat the English as a Sicilian reversed, but the results are often surprising—main lines in the Sicilian Defence correspond to obscure side variations in the English, and vice versa."

The third broad category consists of the non-...e5 and non-...c5 responses, classified A10–19 in ECO. Most often these defences consist of Nf6, e6, and d5 or Bb4 systemic responses by Black, or a Slav-like system consisting of c6 and d5, a direct King's Indian Defence setup with Nf6, g6, Bg7, 0-0, after which c5 and e5 are eschewed, or 1...f5, which usually transposes to a Dutch Defence once White plays d4. All irregular responses such as 1...b6 and 1...g5 are also lumped into this third broad category.

• 1...Nf6 is the most common response to 1.c4, often played to arrive at an Indian Defence. More than half the time, however, Black subsequently elects to transpose into either a Symmetrical Defence with ...c5, or a Reversed Sicilian with ...e5.
• 1...e6 can lead to a Queen's Gambit Declined after 2.Nc3 d5 3.d4, but White often prefers 2.Nf3, which may lead to a variety of openings.
• 1...f5 leads to a Dutch Defence when White follows up with d4. Other choices for White are 2.Nc3, 2.Nf3, and 2.g3, where Black usually plays ...Nf6.
• 1...g6 may lead to a Modern Defense, or after Nf6 and d6 or d5 to the King's Indian Defence or the Grünfeld Defence, respectively, or stay within English lines. Often dubbed the Great Snake Variation.
• 1...c6 can lead to a Slav Defense after 2.d4 d5, but White will often prefer a Caro–Kann Defence with 2.e4 d5, or a Réti Opening after 2.Nf3 d5 3.b3. 1.c4 c6 2.d4 d6 is the Anglo-Slav Opening.
• 1...b6 is the English Defence. This setup involves the fianchetto of the queenside bishop and 2...e6. Often Black will defer the move Nf6, choosing to attack the centre with f5 and/or Qh4. The English grandmasters Tony Miles and Jonathan Speelman have successfully used this opening.
• 1...d5 is the Anglo-Scandinavian Defense.[11] Thought of as inferior to the Scandinavian Defense due to exchanging the c-pawn for a center pawn, in addition to the Scandinavian already having a somewhat suspect reputation.
• 1...g5 is an eccentric response known as Myers' Defense after Hugh Myers's advocacy of it in print and actual play.[12][13][14] It is intended as an improved Grob's Attack; after 2.d4, Black will put pressure on the d4-square with moves such as ...Bg7, ...c5, and ...Qb6.[13][15] According to Nunn's Chess Openings, White obtains a small advantage after 2.d4 Bg7 (offering a Grob-like gambit: 3.Bxg5 c5) 3.Nc3 h6 4.e4.[16] Myers recommended 3...c5 (instead of 3...h6); in response, Joel Benjamin advocates 4.dxc5![13]
• 1...b5 is called the Jaenisch Gambit after Carl Jaenisch.[17] Black obtains no immediate compensation for the sacrificed pawn.[18]