Kan Variation, Modern Variation

The Modern Variation is White's bishop-first answer to the Kan. With 5. Bd3 the e4-pawn is protected by a piece instead of a knight on c3, so the c-pawn stays free to go to c4 later and clamp down on d5. The bishop also points at the kingside, where Black has not yet developed the king's knight.

The most frequent reply is 5...Qc7, a flexible move that watches e5. Other options are 5...b5, which gains queenside space, and 5...Nc6, which develops toward the d4-knight. The Polugaevsky Variation, 5...Bc5, challenges that knight at once and is one of the engine's preferred moves, though it has scored poorly for Black in practice. After 6. Nb3, retreating with 6...Be7 allows 7. Qg4 and kingside pressure, so 6...Ba7 is the usual alternative. The engine also rates the central break 5...d5 highly. The fianchetto 5...g6, the Swiss Cheese Variation, is rare. The engine gives White a slight edge, but in the Lichess database Black wins marginally more often than White, and draws are uncommon.