Key ideas
- White regains the pawn with 6.d4 b5 7.Bb3 d5 8.dxe5 Be6, the main position. Black's knight on e4 is strong but can be challenged, and the pawns on c7 and d5 can become targets.
- 9.c3 is the main move. Black chooses between 9...Be7 (the Classical Defense), 9...Bc5 and 9...Nc5. The Dilworth Variation, 9...Bc5 10.Nbd2 O-O 11.Bc2 Nxf2, gives up two minor pieces for a rook and pawn to open the f-file against White's king.
- 9.Qe2 (the Howell Attack) and 9.Nbd2 are the main alternatives. The Karpov Gambit, 9.Nbd2 Nc5 10.c3 d4 11.Ng5, is a well-known sharp line.
- White's typical ideas are Nbd2 to challenge the e4 knight, Bc2 and Qe2 or Qd3 on the b1-h7 diagonal, and Nd4 aiming at c6 and e6. The a4 lever is used against Black's queenside pawns.
Plans for White
Put pressure on the e4 knight and the d5 pawn. A knight on d4 is strong, the e5 pawn gives kingside space, and the b3 bishop and the e-file can combine against Black's king if the centre opens.
Plans for Black
Use the free pieces: support the e4 knight or reposition it with ...Nc5, and look for ...f6 or ...d4 to free the position. Keep the queen off the d-file when a capture on d5 or d4 might open it.
Watch out
The Tarrasch Trap: 9.c3 Be7 10.Re1 O-O 11.Nd4 Qd7? 12.Nxe6 fxe6 13.Rxe4, and 13...dxe4 opens the d-file for 14.Qxd7, so White wins a piece.
For the wider picture, see the Ruy Lopez guide.