Key ideas
- 2...Nf6 3.e5 Nd5 is a main line. Black's knight attacks e5 at once, and after 4.d4 cxd4 White chooses between 5.Nf3 and 5.cxd4. The e5 pawn gives White space; Black hits it with ...d6 and develops around the active d5 knight.
- 2...d5 3.exd5 Qxd5 4.d4 is the other main road. Black's queen can sit in the centre because the c3 pawn has taken that square from White's knight. A common continuation is 4...Nf6 5.Nf3 Bg4, developing the bishop before ...e6.
- In many lines the game reaches an isolated queen's pawn structure after ...cxd4 and cxd4. White uses the d4 pawn to support Ne5 and a kingside attack; Black blockades on d5 and aims for exchanges.
- 2...e6 3.d4 d5 4.e5 transposes to a French Advance, since White's c3 and Black's ...c5 are standard moves there.
Plans for White
Build the centre with d4. Against 2...Nf6, keep the e5 pawn as a cramping wedge and use Bc4-b3 to pressure the d5 knight. Against 2...d5, develop quickly with Nf3 and Be2 or Bd3 and gain time on Black's queen.
Plans for Black
Counter in the centre at once with 2...Nf6 or 2...d5. In the 2...Nf6 lines, challenge e5 with ...d6; in the 2...d5 lines, bring the light-squared bishop to g4 before playing ...e6.
For the wider picture, see the Sicilian Defense guide.