Classical Variation, Center Attack

With 5. d4 White carries out the idea behind 4. c3 at once. The pawn hits both e5 and the bishop on c5, and if Black ignores it, dxe5 would also drive the f6-knight away. Black therefore takes on d4 in the vast majority of games, since any other reply cedes the center. For centuries this was White's main move against 4...Nf6, and Steinitz relied on it in his world championship matches of 1894 and 1896-97.

After 5...exd4 6. cxd4 the bishop is attacked again, and Black answers 6...Bb4+, gaining time while it retreats. White then chooses between sharp and calmer play. In the gambit 7. Nc3 Nxe4 8. O-O, White gives up the e-pawn for development and open lines against the black king. Black can take the knight with 8...Nxc3, the Greco Variation, or with 8...Bxc3, the Main Line. After 8...Bxc3 the thrust 9. d5 is the Moeller-Therkatz Attack, popular around 1900 but now considered refuted. The blocks 7. Bd2 and, more recently, 7. Nbd2 avoid the material sacrifice and keep the pawn center intact.

The Modern Line, 5...exd4 6. e5, gains space and attacks the f6-knight instead of recapturing. Sveshnikov popularized it, and it has grown in popularity in the 21st century. Black has to counter with 6...d5, hitting the c4-bishop, and the usual sequence is 7. Bb5 Ne4 8. cxd4 Bb6, with the knight posted actively in the center. Anderssen often chose 8...Bb4+ at that point, while Jobava has played 5...exd4 6. e5 d5 7. Be2. White can also leave the d4-pawn alone and gambit with 6. b4, the Dubov Italian, or 6. O-O.

Alternatives to 5...exd4 are rare. 5...Bb6 keeps the bishop on its diagonal and maintains the tension in the center, with results close to those of the main move. 5...d6, holding e5, lets White achieve the ideal center unchallenged and scores poorly for Black. The engine assesses the position as balanced. In online games White wins somewhat more often than Black, and draws are uncommon.