Queen's Indian Defense: Petrosian Variation

About this variation

White plays 4. a3, stopping ...Bb4 so that Nc3 cannot be pinned. It prepares a big center with Nc3 and e4.

The Petrosian Variation is 1. d4 Nf6 2. c4 e6 3. Nf3 b6 4. a3. White prevents ...Bb4, so that the knight can go to c3 without being pinned, and prepares Nc3 and e4 to build a big center. The move was popularized by Tigran Petrosian and later became a favorite of Garry Kasparov.

Black's main replies are 4...Bb7, the classical move, after which 5. Nc3 d5 6. cxd5 Nxd5 7. Qc2 leads to a sharp main line, and 4...Ba6, attacking c4. Black can also play 4...d5, reaching a Queen's Gambit Declined structure, or 4...c5, which usually meets 5. d5 with a Benoni-type center.

White's plans include Nc3, Qc2 and e4, building a strong center, and d5 in some lines to cramp Black. White can also aim for a quick kingside attack if Black castles there without enough defenders.

Black's ideas include ...d5 to stop e4, ...Nxc3 to trade knights and reduce White's control of the center, and ...c5 to challenge d4. Black aims to keep the position balanced and avoid falling behind in space.

A common mistake for Black is to allow e4 without a fight, which gives White a strong center and attacking chances. A common mistake for White is to spend too much time on a3 and Qc2 and fall behind in development.

The Petrosian Variation suits White players who like central control and active play. Black players should know the main line with 4...Bb7 5. Nc3 d5, since it is one of the sharpest tests of the Queen's Indian at a high level.

One concrete line is 4...Bb7 5. Nc3 d5 6. cxd5 Nxd5 7. Qc2 Nxc3 8. bxc3 Be7 9. e4 O-O 10. Bd3 c5, when White has a big center and Black aims to undermine it with ...c5 and ...Nc6. The position is rich and double-edged.

It is one of the main lines of the Queen's Indian Defense.