Three Knights Variation

The Three Knights Variation, 4. Nf3, is also known as the Kasparov Variation: Garry Kasparov used it six times against Anatoly Karpov in the 1985 World Championship match, winning three games and drawing three. White puts the knight on its most natural square and keeps the choice between e3, g3 and other setups open. The position can also come from the Bogo-Indian when White meets 3. Nf3 Bb4+ with 4. Nc3. Alexei Barsov and Nona Gaprindashvili are among its regular exponents.

Black's most frequent reply is 4...d5, which transposes to the Ragozin Defense of the Queen's Gambit Declined. 4...b6 5. Bg5 Bb7 reaches a hybrid of the Nimzo-Indian and the Queen's Indian. 4...O-O and 4...c5 keep the game in Nimzo-Indian territory. After 4...c5, 5. e3 transposes to the Rubinstein System, and 5. d5 is the Korchnoi Variation. The main move is 5. g3, and 5. g3 cxd4 6. Nxd4 O-O 7. Bg2 d5 8. cxd5 Nxd5 dissolves White's center, though the g2-bishop presses on Black's queenside, sometimes backed by 9. Qb3. The engine rates the position as balanced, and online results are nearly even.