Steinitz Variation, Boleslavsky Variation

The Boleslavsky Variation is the main line of the Steinitz Variation. After 5. f4 c5 6. Nf3 Nc6, the move 7. Be3 adds a third defender to d4, holding the pawn chain intact against Black's pressure. It also keeps the d1-h5 and a1-f6 lines flexible, so White can follow with Qd2 and long castling or with Be2 and short castling. The bishop on e3 can become a target for a black queen on b6 or a knight jumping into g4 or f5, and much of the play revolves around whether White can keep the d4-e5-f4 wedge stable.

Black's three main replies occur with similar frequency. 7...Qb6 hits b2 and d4 immediately. 7...cxd4 8. Nxd4 releases the central tension, after which Black can choose between ...Qb6 and ...Bc5. 7...a6, the engine's preferred move, prepares queenside expansion with ...b5, for example 8. Qd2 b5. The engine gives White a slight edge, but practical results are close to even, with White marginally ahead in online games.