Kan Variation, Knight Variation

With 5. Nc3 White develops the queen's knight to its most natural square, covering d5 and adding support to a future e5 push, rather than committing the bishop to d3 or setting up a Maróczy Bind with c4. The main practical consequence concerns Black's king's knight. If it goes to f6 at once, e5 chases it away and leaves a hole on d6, so Black generally spends a tempo restraining the e-pawn before deciding where the knight belongs. The engine gives White a slight edge, yet in the Lichess database Black wins a little more than half of the games, and draws are uncommon.

The usual answer, chosen in roughly half of the games, is 5...Qc7, the standard Kan treatment, in which the queen watches e5 and Black keeps the remaining pieces flexible. The Wing Attack, 5...b5, aims at queenside play with ...b4 against the c3-knight and ...Bb7 pressing on e4, and is normally met by 6. Bd3. Alternatively, 5...Nc6 transposes to the Taimanov Variation, where results are closer to even, and 5...d6 leads to the Scheveningen.