Key ideas
- The Spanish Variation, 4.Bb5, is the main line. Black can mirror it with 4...Bb4 (the Double Spanish), play 4...Bc5, or choose the Rubinstein Variation, 4...Nd4, a pawn offer that is considered one of Black's most reliable answers.
- The Scotch Variation, 4.d4, opens the centre. After 4...exd4 5.Nxd4 Bb4 6.Nxc6 bxc6 7.Bd3 d5, Black accepts doubled c-pawns in return for active pieces and a central pawn on d5.
- In the Symmetrical Variation (4.Bb5 Bb4 5.O-O O-O 6.d3 d6), the pin Bg5 and the exchange ...Bxc3, which leaves White with doubled c-pawns, are the key themes. Breaking the symmetry at the right moment decides the game.
- Quieter tries include 4.g3, the Glek System, and 4.a3, which keeps ...Bb4 out. The Halloween Gambit, 4.Nxe5, gives a knight for a pawn and a big centre, but it is considered unsound.
Plans for White
In the Spanish lines, castle, play d3, and use the pin Bg5 or the manoeuvre Ne2-g3 to build pressure on the kingside. Choose 4.d4 if you prefer an open centre.
Plans for Black
Answer 4.Bb5 with 4...Nd4 or 4...Bb4, and answer 4.d4 by taking on d4 and pressuring e4. Do not copy White's moves for too long, since in symmetrical positions the side that moves first often strikes first.
Watch out
Copying can be fatal. After 4.Bb5 Bb4 5.O-O O-O 6.d3 d6 7.Bg5 Bg4 8.Nd5 Nd4 9.Nxb4 Nxb5 10.Nd5 Nd4 11.Qd2 Qd7? 12.Bxf6 Bxf3 13.Ne7+ Kh8 14.Bxg7+ Kxg7 15.Qg5+ Kh8 16.Qf6# White mates, and 13...Qxe7 14.Bxe7 only saves the king at the cost of the queen.