Classical Variation, La Bourdonnais Variation

The La Bourdonnais Variation arises when Black meets the Classical Variation's c3 with the restrained 4...d6 rather than counterattacking e4 with 4...Nf6. After 5. d4 exd4 6. cxd4 Bb6, the bishop retreats to b6 instead of giving the check 6...Bb4+. This avoids the exchanges and gambit play of the Center Attack and keeps the bishop on the a7-g1 diagonal, where it eyes d4. The price is that White keeps intact pawns on d4 and e4 side by side and a clear space advantage, while Black's d6-pawn holds the center from behind and the half-open e-file offers some counterplay against e4.

The engine gives White a slight edge, yet in online play the results are almost exactly even. The most common continuation is 7. O-O, which completes development before committing the center. 7. Nc3 brings a further defender to e4. The space-gaining 7. d5 drives the c6-knight away but gives up the flexibility of the pawn duo. Among the engine's preferred moves are 7. Bb5, which pins the knight and adds pressure to the d4-e4 center, and 7. h3, a prophylactic move.