Austrian Attack, Weiss Variation

With 6. Bd3 White completes kingside development before committing the center. The bishop guards e4, eyes the kingside where Black has castled, and leaves the e5 push in reserve rather than playing it at once as in the Unzicker Attack. It is the most frequently chosen sixth move after 5...O-O. Fischer was among the White players who switched to it after a loss in the 6. Be2 line. Because Black has little space, he needs to break with ...c5 or ...e5 before White's buildup becomes overwhelming.

The three main replies are roughly equally popular in online play. 6...c5 attacks d4 directly. 6...Nc6 is the traditional choice and prepares ...e5, but it came to be seen as giving Black few winning chances. That opinion helped popularize 6...Na6 in the 1980s, with the knight heading for c7 to support ...Rb8 and ...b5 on the queenside. 6...Bg4 pins the f3 knight and also prepares ...e5. Results online are close to even, while engines give White a slight edge.