Key ideas
- 4.Ng5 d5 5.exd5 Na5 is the main line. Black gives a pawn to chase the bishop: 6.Bb5+ c6 7.dxc6 bxc6 8.Be2 h6 9.Nf3 e4 10.Ne5 leaves White a pawn up but Black ahead in development and space.
- Other answers to 4.Ng5 are the sharp 5...Nd4 (the Fritz) and 5...b5 (the Ulvestad), and the Traxler Counterattack 4...Bc5, which ignores f7 altogether.
- 4.d3 is the modern positional choice. It defends e4, avoids the gambits and leads to slow Italian structures with c3, O-O, Re1 and Nbd2-f1-g3.
- 4.d4 exd4 5.O-O opens the centre. After 5...Nxe4 6.Re1 d5 7.Bxd5 Qxd5 8.Nc3 White regains material through the pins on the e-file, while 5...Bc5 6.e5 leads to the Max Lange Attack.
Plans for White
With 4.Ng5 you win a pawn but spend time; after 5...Na5, 6.Bb5+ keeps the bishop, and the task is to untangle and hold the extra pawn. With 4.d3, keep the centre closed and play a long manoeuvring game.
Plans for Black
Against 4.Ng5, know 4...d5 5.exd5 Na5: development and the ...e4 push are your compensation. Against 4.d3, ...Be7 or ...Bc5, ...d6, ...O-O and ...a6 give a solid position.
For the wider picture, see the Italian Game guide.