Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6/4. Ba4/4...Nf6/5. O-O/5...Nxe4/6. d4

Open Spanish Spanish game via Morphy defence transposition via Berlin defence → Rosenthal variation 6. d4 White is threatening to win back material by capturing Black's e-pawn. More importantly, they threaten to create dangerous attacks on the e-file while Black is still uncastled. Black needs to complete their development, and if possible reinforce the crusading knight on e4. The immediate 6...d5? would leave the c6-knight pinned, allowing the powerful 7. Nxe5!. To get to grips with the situation, Black needs 6...b5 to prepare ...d5 by chasing the bishop away. If Black is unconcerned with opening the e-file, they can accept an extra pawn with 6...exd4?!, the chaotic Riga variation, which leads to a wonderful mess. 6...Be7!? is a semi-useful move. After 7. Re1 this leads to a big liquidation of the centre: 7...b5 8. Rxe4 d5 9. Nxe5 Nxe5 10. Rxe5 bxa4+ and Black can't castle without dropping the e7 bishop. Unlike in the Berlin defence, 6...Nd6? does not come with tempo on White's bishop and so does not work. Theory table References See also Ruy Lopez