Classical Variation

The Classical Variation, also called the Cordel Defense or Classical Defense, arises when Black meets 3. Bb5 with 3...Bc5. The bishop goes to its most active diagonal and eyes f2, ignoring the indirect pressure on c6. It is among the oldest replies to the Ruy Lopez. Its drawback is that the latent threat to e5 remains, and White's standard c3 and d4 advance can gain time by hitting the bishop. For this reason it has never been a main line. Boris Spassky and Boris Gulko have used it occasionally, but today it is a minor sideline, far more frequent in amateur and online games than at elite level.

4. c3, the Central Variation, is the most direct test, preparing d4 at once. The solid 4...Nf6 is common, and after 5. O-O the game transposes to the Beverwijk Variation of the Berlin Defense. 4...Bb6, the Charousek Variation, withdraws the bishop before d4 arrives. 4...d5 is the Konikowski Gambit. 4...f5, the Cordel Gambit, produces sharp play, and 5. d4 is regarded as the strongest answer; its main line runs 5...fxe4 6. Bxc6 dxc6 7. Nxe5 Bd6 8. Qh5+ g6 9. Qe2. The passive 4...d6 is poor because of 5. d4.

4. O-O is the most frequent choice in the Lichess database and the engine's top move. Castling puts the king on the bishop's diagonal, however, and the rook may have to stay on f1 to cover f2. Black's most common answer is the more positional 4...Nd4, as in 5. Nxd4 Bxd4 6. c3 Bb6 7. d4 c6, with ...d6 to follow. 4...Nf6 again reaches the Beverwijk, and 4...Nge7 is another established option. The same bishop development can also arise from the Berlin move order 1. e4 e5 2. Nf3 Nc6 3. Bb5 Nf6 4. O-O Bc5. Then 5. c3 is the Zukertort Gambit, and 5...O-O 6. d4 Bb6 7. Bg5 is the Modern Main Line.

Among the other tries, 4. Bxc6 is the second most popular move in online play, while the Spanish Wing Gambit 4. b4 is rare. The fork trick 4. Nxe5 is also possible. After 4...Nxe5 5. d4, White attacks both minor pieces, but Black can sidestep this with 4...Qe7 or 4...Qg5. Engines give White a slight edge. Practical results are close to even, with very few draws.