King's English Variation, Four Knights Variation, Fianchetto Line

With 4. g3 White prepares Bg2, placing the bishop on the long diagonal to bear on d5 and the queenside, and then castles short. ECO assigns the line its own code, A29. Black's three main replies are almost equally popular. 4...Bc5 develops actively toward f2, and after 5. d3 d6 6. Bg2 Black settles into a compact setup known as the line with ...d6. 4...d5 strikes in the center at once. After 5. cxd5 Nxd5 6. Bg2 the knight either retreats with 6...Nb6 or stays put while Black plays 6...Bc5, giving a reversed Dragon structure in which White has an extra tempo. 4...Bb4 pins the c3-knight, keeping ...Bxc3 and ...e4 in reserve. The Delayed ...Nc6 line reaches a related position by another order, 1. c4 e5 2. Nc3 Nf6 3. g3 Bb4 4. Bg2 O-O 5. Nf3 Re8 6. O-O e4 7. Nd4 Nc6.

The engine rates the position as balanced and prefers 4...Bb4, 4...d5 and the rarer 4...Nd4. White scores somewhat better overall, and 4...Bb4 gives Black the best practical results of the main replies.