Petrosian Variation

The Petrosian Variation arises from the Classical King's Indian when White answers 6...e5 with an immediate 7. d5 instead of castling. Locking the center at once keeps White's king flexible and frees the c1-bishop for Bg5. From there it pins the f6-knight, which makes ...f5 harder to prepare. The line is named after Tigran Petrosian, who used it often in the 1960s, and Vladimir Kramnik adopted it extensively in the 1990s. The strategic plans broadly match those of the main lines: White prepares c4–c5, and Black seeks kingside activity.

The most common reply is 7...a5, the Stein Defense, after which White usually pins with 8. Bg5. Early practice saw Black chase the bishop with ...h6 and ...g5. This approach also appears in the Keres Defense, 7...Nbd7 8. Bg5 h6 9. Bh4 g5 10. Bg3 Nh5 11. h4, where White strikes at once at the advanced pawns. Black later preferred to slow c4–c5 first with ...Na6, ...Qe8 and ...Bd7, and only then turn to the kingside. Joe Gallagher has recommended 7...Na6, which pursues similar ideas. Engines give White a slight edge, while practical results are close to even.