Sicilian Defence (Open Sicilian)

White increases their control of the d4 square: the conventional plan is to follow with 3. d4 cxd4 4. Nxd4 and open the position.

Black's attention must now turn to their development: determining how to release their bishops, or first developing their knight. The main lines are 2...d6, accounting for almost half of games, and 2...Nc6 and 2...e6, each about half as popular as 2...d6.

At some point Black would like to do something with their bishops, and that requires they make a pawn move first.

2...d6 is the mainline. This releases the queen's bishop on the c8-h3 diagonal, and because of the pawn on d6, it usually means king's bishop must fianchetto to g7. 2...d6 also controls e5, ensuring Black can play ...Nf6. After 3. d4 cxd4 4. Nxd4 this usually leads to the Najdorf, Dragon, Classical, or Scheveningen Sicilians. A sideline is 3. Bb5+, the Moscow variation.

2...e6, sometime called the French Sicilian, opens the a3-g8 diagonal for the king's bishop, and since the e6 pawn obstructs the queen's bishop, in these lines it is usually fianchettoed to b7. The typical ...e6 Sicilians are the Kan, Taimanov, or Four Knights variations. This can also transpose to the Scheveningen with ...d6.

Preparing to fianchetto straight away is less common. 2...g6, preparing ...Bg7, is the Hyper-accelerated dragon Sicilian (accelerated over the regular Dragon in that Black hasn't played ...d6 yet, and hyper-accelerated in that Black hasn't played ...Nc6 yet either).

2...b6!? to prepare Bb7, called the Katalimov, is non-standard. It may transpose into a Kan or other ...e6 Sicilian, though Black will have lost a tempo if they intend to play ...a6 and ...b5.

2...Nc6 is the most traditional move, sometimes called the Old Sicilian. Black develops the knight to its natural square. It reserves options in the centre and keeps an eye on d4. After 3. d4 cxd4 4. Nxd4 this usually leads to the Sveshinkov, Accelerated Dragon or Kalashnikov Sicilians. However, this allows White to enter the sideline 3. Bb5, the Rossolimo attack.

The most significant departure from the above main lines is 2...Nf6, the Nimzowitsch variation. As in Alekhine's defence, Black attacks the e-pawn to tempt it forward.

2...a6 is the O'Kelly variation. ...a6 is played in many Open Sicilian lines eventually to control the b6 square. This move order creates some novel possibilities, e.g. after 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 e5! White's knight cannot go to b5, so must retreat, and as Black hasn't played ...d6 yet (as in the Najdorf) they can play ...Bb4!. It can restrain some of White's longer-term plans and provide the springboard for ...b5.

Another move-order anomaly is 2...Qc7 the Quinetros variation. Black's queen ends up on c7 in many Sicilians and this can transpose, e.g. 3. d4 cxd4 4. Nxd4 a6 5. Nc3 e6 transposes to the Kan Sicilian.

2...e5? is the Jalalabad variation where Black immediately throws away their e-pawn.

2...b5? is the Polish gambit. Black gives up their b-pawn to 3. Bxb5.

For explanation of theory tables, see theory table and for notation, see algebraic notation.

1. e4 c5 2. Nf3

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Wikipedia has related information at Sicilian Defence

• Nunn's Chess Openings. 1999. John Nunn (Editor), Graham Burgess, John Emms, Joe Gallagher. ISBN 1-8574-4221-0.

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.