Pawn Push Variation

The Pawn Push Variation meets 1...Nf6 with 2. d5. Because Black has not played ...d5, White can advance the queen's pawn a second step, where it is protected by the queen and takes squares from Black's minor pieces. The cost is that the pawn stands alone. Neither c4 nor e4 supports it, and White has spent two tempi on a single unit that Black can attack. Reference sources treat the move as dubious. Engines nonetheless rate the position as roughly balanced, and on Lichess Black scores somewhat better than White.

The most direct answer, and the engine's first choice, is 2...e6. If White then plays 3. dxe6 fxe6, the exchange leaves White with no central pawn at all. Engines also suggest 2...c6 and 2...b5, which attack the pawn's support from the other side or claim queenside space. In practice 2...d6 is the most common reply, with 2...g6 and 2...e6 next. The knight retreat 2...Ng8, the Montevideo Defense, is the one popular choice after which White scores better. 2...c5 leads to the Benoni Defense: Benoni-Indian Defense.