Spanish Variation, Classical Variation

Instead of mirroring White with 4...Bb4, Black develops the bishop to c5, where it eyes f2. This diagonal is what keeps e5 defended. After 5. Bxc6 dxc6, the most frequent continuation, the pawn grab 6. Nxe5 fails to 6...Bxf2+ 7. Kxf2 Qd4+, forking king and knight. After 8. Ke2 Qxe5 Black regains the piece, and White's king is stuck in the center of an open position without the right to castle. The line has a long pedigree. It occurred in the game Louis Paulsen–Paul Morphy at the First American Chess Congress in 1857.

White's other main tries are 5. O-O and the quiet 5. d3. A more direct option is the center fork 5. Nxe5 Nxe5 6. d4, which wins back the piece and claims central space. After 5. O-O O-O, the Bardeleben Variation, 6. Nxe5 Nxe5 7. d4 Bd6 8. f4 Nc6 9. e5 Bb4, leads to sharper play. Engines regard the position as roughly balanced. In online games, where 4...Bc5 is Black's most popular reply to 4. Bb5, the two sides score almost evenly and draws are rare.