Key ideas
- After 3.dxe5 the main move is 3...Ng4, hitting e5 again. Black regains the pawn with ...Nc6, and often ...Qe7 or ...Bb4+, then plays against White's slightly loose position.
- The Rubinstein Variation, 4.Bf4, defends the pawn with a piece. A typical line is 4...Nc6 5.Nf3 Bb4+ 6.Nbd2 Qe7, and Black later plays ...a5 and may swing the rook into the attack along the sixth rank with ...Ra6.
- In the Alekhine Variation, 4.e4, White lets Black regain the pawn with 4...Nxe5 and builds a big centre, chasing the knight with f4. White gains space but has to watch the loosened king.
- The Fajarowicz Variation, 3...Ne4, is sharper. Black doesn't win back e5 straight away and relies on fast development and tactics instead.
Plans for White
Develop calmly and give the pawn back on your terms. Meet ...Bb4+ with Nbd2 or Nc3, keep the bishop pair when you can, and use the extra queenside space for a long-term edge.
Plans for Black
Win back e5 with ...Nc6 and ...Qe7, develop quickly and use your pieces actively. If the activity fades, White's extra space usually tells.
Watch out
In the Rubinstein Variation, after 4.Bf4 Nc6 5.Nf3 Bb4+ 6.Nbd2 Qe7 7.a3 Ngxe5, White must not take the bishop: 8.axb4?? Nd3# is mate, because the queen on e7 pins the e2 pawn.

