Key ideas
- After 5.e4 Nxc3 6.bxc3 Bg7, White chooses between 7.Bc4 with Ne2 (the Classical Exchange) and 7.Nf3 (the Modern Exchange). The knight on e2 cannot be pinned by ...Bg4 and supports d4 without blocking the f-pawn.
- A key Classical position arises after 7.Bc4 c5 8.Ne2 Nc6 9.Be3 O-O 10.O-O Bg4 11.f3 Na5. White can play 12.Bxf7+ (the Seville Variation) or 12.Bd3 cxd4 13.cxd4 Be6, when 14.d5 Bxa1 15.Qxa1 offers the exchange for a dangerous initiative on the dark squares.
- In the Modern Exchange, 7.Nf3 c5 is met by 8.Rb1, taking the rook off the long diagonal and eyeing b7, or by 8.Be3 with Qd2 and Rc1. The pawn-grab line 8.Rb1 O-O 9.Be2 Nc6 10.d5 Bxc3+ is among the sharpest.
- If Black exchanges with ...cxd4 and cxd4, Black has a queenside majority (two pawns against one) and White a central majority. White's d5 push and Black's passed queenside pawn in the endgame are the long-term themes.
Plans for White
Keep d4 protected and the centre mobile. A timely d5, gaining space and blocking the g7 bishop, is the main positional idea; f4 and f5 with a kingside attack is the dynamic alternative. Avoid endgames in which Black's queenside majority can run.
Plans for Black
Put maximum pressure on d4 with ...Bg7, ...c5, ...Nc6, ...Bg4 and ...Qa5 or ...Qb6, and exchange on d4 at the right moment to create the queenside majority. Trading queens often suits Black, since White's centre loses much of its attacking value in an endgame.
For the wider picture, see the Grünfeld Defense guide.