Byrne Variation

The Byrne Variation, 4. Bg5, was brought into practice by Robert Byrne in the 1960s. White brings out the dark-squared bishop before deciding on a pawn setup. From g5 it bears on the f6-knight and supports the familiar plan of Qd2 followed by Bh6 to trade Black's fianchettoed bishop. That plan can transpose into the Be3 and Qd2 systems. A less common treatment is 4...Bg7 5. f4, followed by Nf3, Bd3 and O-O, as Byrne himself played it. This gives a version of the Austrian Attack in which the bishop already stands outside the pawn chain rather than being shut in by f2-f4.

The natural 4...Bg7 accounts for the vast majority of games. Some sources regard 4...c6 as the more adaptable reply. Black holds back ...Bg7 so that, if White carries out Qd2 and Bh6, the bishop can be exchanged without Black having spent a tempo on it. Meanwhile Black seeks queenside activity with ...b5 and ...Qa5. The rarer 4...h6 puts the question to the bishop at once. Engines give White a slight edge, and White scores somewhat better than Black in online games.