Key ideas
- 3...c5 4.c3 Nc6 5.Nf3 Qb6 is the main line. Black piles up on d4 with the knight, the queen and often ...cxd4 and ...Nge7-f5 or ...Nh6-f5; White holds it with c3, Nf3 and Be2 or Bd3.
- 6.a3 prepares b4 to gain queenside space and stop ...Bb4+. Black often answers 6...c4 to close the queenside, or 6...Nh6 heading for f5.
- The Milner-Barry Gambit, 6.Bd3 cxd4 7.cxd4 Bd7 8.O-O Nxd4 9.Nxd4 Qxd4 10.Nc3, gives up the d4 pawn for development and attacking chances.
- Black's light-squared bishop can be exchanged with ...Bd7 and ...Bb5, and once the pieces are ready, ...f6 attacks the head of the pawn chain on e5.
Plans for White
Secure d4 first and attack later. Keep the e5 pawn as a cramping wedge, develop with Nf3 and Be2 or Bd3, and turn to the kingside once the centre is safe. b4 gains queenside space in many lines.
Plans for Black
Attack d4 with every piece: ...c5, ...Nc6, ...Qb6 and a knight on f5. When White has committed, ...f6 opens the f-file and challenges e5.
Watch out
After 5...Qb6 6.Bd3 cxd4 7.cxd4, grabbing with 7...Nxd4? 8.Nxd4 Qxd4?? loses the queen to 9.Bb5+, which uncovers White's queen on d1 against the queen on d4. That is why Black plays 7...Bd7 first.
For the wider picture, see the French Defense guide.