Key ideas
- 4.e5 c5 5.a3 Bxc3+ 6.bxc3 Ne7 is the main line. White has doubled c-pawns and the bishop pair; Black has a sound structure and plays against c3 and a3 with ...Qa5, ...Nbc6 and ...Bd7.
- 7.Qg4 attacks g7 and leads to the Poisoned Pawn: 7...Qc7 8.Qxg7 Rg8 9.Qxh7 cxd4. Black gives up the kingside pawns for central pressure and play against c3, and both kings face danger.
- 7.Nf3 and 7.a4 make up the Positional Variation. White keeps the structure, prepares Ba3 or Bd2 for the dark-squared bishop, and aims to open the position for the bishops later.
- White can avoid the main line with 4.exd5 exd5, a symmetrical structure, or 4.Ne2, which offers the e4 pawn. 5...Ba5, the Retreat Variation, keeps Black's bishop instead of exchanging it.
Plans for White
Use the bishop pair and the dark squares Black has given up. Qg4 against g7, a4 and Ba3 against the e7 knight and f8, and f4-f5 or dxc5 to open lines are typical ideas. Do not let Black win the c3 or a3 pawns for free.
Plans for Black
Play against the doubled c-pawns with ...Qa5 or ...Qc7, ...Nbc6 and ...Bd7, and consider ...c4 to fix them. The light-squared bishop is still the problem piece, so ...b6 and ...Ba6 to exchange it is a useful plan.
For the wider picture, see the French Defense guide.