Chess Opening Theory/1. e4/1...c5/2. Nf3/2...d6/3. d4/3...cxd4/4. Nxd4/4...Nf6/5. Nc3/5...e6/6. g4

=Scheveningen Variation, Keres Attack= White's 6. g4 begins the Keres Attack, a sharp and important line in the Scheveningen Variation.

Black's previous move, 5...e6, boxes in his light squared bishop and relinquishes control over the g4 square. Now, White advances his g pawn with the idea of following with 7. g5, pushing black's f knight back and winning more space on the kingside. Note that against the Sicilian, White often opens up a kingside pawn storm, such as in the English Attack, and 6. g4 furthers that goal well.

Black's most common response, therefore, is 6...h6, preventing the g pawn from advancing. Other responses, such as 6...Nc6, do not discourage the g pawn push, and are therefore usually followed by 7. g5 Nd7. Now black's kingside knight has been pushed back into a much more passive position and white's pawns are dangerously close to black's kingside, if black chooses to castle there. After 6...h6 Black should certainly not proceed to castle kingside quickly against this line.

Attempting to counterattack with 6...e5 is easily met by 7.Bb5+ Bd7 8.Bxd7+ Qxd7 9.Nb3. White has traded off light squared bishops, and is preparing to set up the standard English Attack. Note that this is one reason that many Scheveningen players use a Najdorf move order first and transpose to the Scheveningen. In this case, the presence of the a6 pawn discourages Bb5+, and lines here in which white plays g4 are referred to as the Perenyi Attack rather than the Keres Attack.

Theory table
'''1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5. Nc3 e6 6. g4'''