Central Variation, Modern Defense

The Modern Defense answers the Central Variation, 3. e4, with 3...Nc6. The knight goes straight for d4, which White has left without a defender by playing e4 before Nf3. Instead of challenging the center with a pawn, as in the McDonnell Defense (3...e5), Black relies on piece pressure in the manner of the Chigorin Defense. White has not yet recovered the c4 pawn, so each tempo spent shoring up the center gives Black more time.

The most common reply is 4. Nf3, which protects d4 and keeps the pawn duo intact. Nearly as frequent is 4. d5, which gains space and drives the knight away with tempo, leaving a more closed center. Both moves score well for White. Engines also suggest 4. Be3. The immediate 4. Bxc4 regains the pawn but gives the center less support, and in online games it is the only main option in which Black outscores White. The engine gives White a slight edge after 3...Nc6. The line is a less common alternative to the main defenses against 3. e4.