Three Knights Variation, Petrosian System

The Petrosian System, 5. Bg5, also known as the Taimanov Variation, develops the bishop to pin the f6-knight and adds pressure on d5 rather than building the broad center the Grünfeld invites. Yasser Seirawan has favored it. The most common reply is 5...Ne4, which attacks the bishop and the c3-knight at once. Castling with 5...O-O and the solid 5...c6 are the main alternatives. The engine rates the position as roughly balanced.

After 5...Ne4 White chooses between 6. Bh4 and 6. cxd5. Against 6. Bh4, Black can play 6...Nxc3 7. bxc3 dxc4 and give White doubled c-pawns. After 6. cxd5 Nxg5 7. Nxg5 e6, the quieter 8. Nf3 exd5 produces a structure like the Exchange Queen's Gambit Declined. White pursues a minority attack with b4-b5, and Black plays on the kingside with ...f5-f4 and ...g5. The sharper 8. Qd2 exd5 9. Qe3+ seeks attacking chances. The pawn grab 6. Nxd5? is an error, since 6...Nxg5 7. Nxg5 e6 wins a piece.