Kan Variation

The Kan Variation, also known as the Paulsen Variation after Louis Paulsen, arises when Black answers the Open Sicilian with 4...a6 instead of 4...Nc6 (the Taimanov) or 4...Nf6. The move takes b5 away from White's knights and prepares a later ...b5 expansion. Black keeps the minor pieces at home for the moment, aiming to set the pawns on light squares and cover the dark squares with pieces, and chooses a deployment only once White has shown a setup. The flexibility comes at a cost in development, which White tries to exploit.

In the Lichess database 5. Nc3, the Knight Variation, is the most frequent reply. Here ...Nf6 is often premature because e5 drives the knight away and leaves a hole on d6, so Black usually first restrains the e-pawn. The main Kan treatment is 5...Qc7, while 5...Nc6 transposes to the Taimanov and 5...d6 to the Scheveningen. The Wing Attack, 5...b5, seeks immediate queenside activity with ...b4 against the c3-knight and ...Bb7 on the long diagonal; White normally meets it with 6. Bd3, defending e4.

The Modern Variation, 5. Bd3, protects e4 with the bishop and leaves the c-pawn free to advance. The Polugaevsky Variation, 5...Bc5, puts the question to the d4-knight; after 6. Nb3 the retreat 6...Be7 allows 7. Qg4, which creates difficulties on Black's kingside, so 6...Ba7 is the other option. Fianchetto setups also appear: 5...g6 is the Swiss Cheese Variation, and 5...Nf6 6. O-O d6 7. c4 g6 is the Gipslis Variation.

With 5. c4, the Réti Variation, White adopts a Maróczy Bind, clamping down on d5 and limiting Black's freeing breaks, which leads to slower, more positional play. The Bronstein Variation, 5...Nf6 6. Nc3 Bb4 7. Bd3 Nc6, uses the pin on the c3-knight to pressure e4, while 5...g6 is classified as the Hedgehog Variation.

The engine rates the position as a slight edge for White, with 5. Bd3, 5. c4 and 5. Nc3 all among its preferred moves. In practice Black has done well: in the Lichess database Black wins slightly more than half of the games reaching the position, and draws are rare. ECO classifies the variation as B41.