Key ideas
- After 4...Bxb4 5.c3 the bishop must move again. 5...Ba5 is the main line, keeping the bishop on the a5-e1 diagonal; 5...Be7, 5...Bc5 and 5...Bd6 are the other retreats.
- White follows with d4 and O-O, with Qb3 against f7 and Ba3 to keep Black's king in the centre. If Black takes everything, the Compromised Defense 5...Ba5 6.d4 exd4 7.O-O dxc3 gives White a large lead in development for three pawns.
- Lasker's Defense, 5...Ba5 6.O-O d6 7.d4 Bb6, returns the pawn: after 8.dxe5 dxe5 9.Qxd8+ Nxd8 10.Nxe5, material is level and the queens are gone, which takes much of the sting out of the gambit.
- Declining with 4...Bb6 is safe and leads to calmer play, where White's b4 pawn has gained queenside space but has also loosened the queenside.
Plans for White
Play for development and the centre, not the pawn: c3, d4, O-O, Qb3 and Ba3 are the standard moves. Open lines quickly before Black castles, and watch f7 and the e-file.
Plans for Black
Choose between keeping the pawn and returning it. 5...Ba5 with ...d6 and ...Bb6 is the solid route. Castling early and keeping the centre closed shut down most of White's tricks.
For the wider picture, see the Italian Game guide.