Kennedy Variation, Main Line

The main line arises when Black answers the gain of time 4. f4 with 4...Ng6 rather than 4...Nc6, the Riemann Defense. From g6 the knight attacks the f4 pawn, which the c1 bishop protects, and keeps watch over e5. After the exchange on e5, White has pawns on e4 and f4 against Black's remaining d-pawn, and the d- and e-files are half-open. White hopes to use the extra central pawns and open f-file prospects to gain space and initiative. Black aims to develop quickly and pressure the advanced pawns, especially e4 and f4. The engine gives White a slight edge, and White scores clearly better than Black in practice.

By far the most common continuation is 5. Nf3, which develops and adds a defender to e5 and h4. The bishop moves 5. Be3 and 5. Bc4 are each seen in roughly an eighth of games. The latter, aiming at f7, produces the best results for White. Engine preferences also include 5. Nc3 and 5. Ne2.