Chess Opening Theory/1. e4/1...c5/2. Nf3/2...d6/3. d4/3...cxd4/4. Nxd4/4...Nf6/5. Nc3/5...Nc6

This position may either be reached from the 2...Nc6 or 2...d6 Sicilians. Black's set up with ...Nc6, ...d6, and ...Nf6 is the classical Sicilian defence. The pawn on ...d6 prevents e5 to kick Black's knight from f6 and opens a line for Black's queen's bishop to develop.

Next White looks to develop their bishops.

6. Bc4 is the Sozin attack. Black usually plays 6...e6, and the line continues 7. Be3 Be7 8. Qe2 a6 9. O-O-O O-O. 6...Qb6 is an alternative.

6. Bg5, the Richter-Rauzer variation, is White's most popular response, pinning a knight and preparing to castle long and attack on the king's side. The main line continues 6...e6 7. Qd2 Be7 8. O-O-O O-O 9. f4. 6. Bg6 prevents 6...e5 for tactical reasons, beginning with 7. Bxf6 gxf6 8. Nf5 and getting progressively dark for Black from there.

1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 d6

Wikipedia has related information at Sicilian Defence.

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