Ruy Lopez: what to play after Bb5?

The position reached after e4 e5 Nf3 Nc6 Bb5 constitutes the starting point of the Ruy Lopez, classified under ECO code C60. Black typically chooses between the solid Berlin Defense with Nf6 or the Morphy Defense with a6 to challenge the b5. While a6 is the most frequent choice in 26.2% of recorded games, the engine evaluation slightly prefers Nf6 as the most precise continuation to maintain the balance.

The Berlin Defense and Morphy Variation

The move Nf6 is played in 20.6% of the 87 million games recorded at this position and carries an engine evaluation of +0.17. It prioritizes development and puts immediate pressure on the e4, often leading to the "Berlin Wall" endgame if White chooses to simplify. Alternatively, a6 is the most popular human response, appearing in 38 million games. This move forces the b5 to declare its intentions immediately, usually leading to the main line sequence a6 Ba4 Nf6 O-O Nxe4 d4.

Classical and Modern Alternatives

Aside from the two primary systems, Black frequently employs the Classical Defense with Bc5. This move is seen in 12.7% of games and carries an evaluation of +0.44. It develops the dark-squared bishop to an active diagonal before White can solidify the center with c3. White typically responds with the sequence Bc5 c3 Nf6 O-O O-O d4, leading to complex middlegame struggles where White maintains a slight statistical edge, scoring 51.8% from this branch.

Strategic Implications of the Position

The Ruy Lopez exerts long-term pressure on the e5 pawn by attacking its defender, the c6. While the engine suggests Be7 and g6 as viable alternatives with evaluations of +0.43 and +0.56 respectively, these moves have no recorded games in the provided dataset, suggesting they are significantly less common in master-level practice. Most high-level play revolves around the tension created by the b5, forcing Black to decide whether to expand on the queenside or focus on rapid kingside mobilization.