The Najdorf variation of the Sicilian opening is one of the most complex and respected of all chess openings.

It begins thus:

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6:

Black's fifth move, a6, aims to deny White the b5 square for his knights and light-colored bishop while maintaining maximum flexibility against White's attack.

The oldest, sharpest response by White is an immediate 6. Bg5, generally countered by e6, followed by 7. f4, hoping to exploit the pin on the knight. The simplest response by Black is Be7, leading to quick castling by both sides. However, Black can also play Qb6!?, leading to the extremely complicated Poisoned Pawn variation (8. Qd2, Qxb2, 9. Rb1 or Nb3, Qa3). Black is up a pawn but very underdeveloped: however, his pieces can quickly become mobile and his position is hard for White to break.

Because of the success of various players with in these variations (notably Bobby Fischer and Garry Kasparov), White now often plays 6. Be2 and goes for a quieter, more positional game. However, 6. Bc4, 6. Be3 and 6. f4 are also respected methods for White to continue his onslaught.