Key ideas
- 3...c5, the Open System, often leads to an isolated queen's pawn for Black after 4.exd5 exd5 5.Ngf3 Nc6 6.Bb5 Bd6 7.dxc5 Bxc5 8.O-O Ne7. White aims to blockade d4 with a knight; Black has free piece play.
- 4.exd5 Qxd5, the Chistyakov Defense, is the other way to meet 4.exd5. Black recaptures with the queen, avoids the isolated pawn and accepts some loss of time.
- 3...Nf6 4.e5 Nfd7 5.Bd3 c5 6.c3 Nc6 7.Ne2 is the Closed Variation, with a French Advance-type structure. The e2 knight supports d4 and can go to f4, and White can also play f4 to reinforce e5.
- 3...Be7, 3...Nc6 (the Guimard) and 3...a6 are flexible alternatives that wait to see how White develops before choosing a structure.
Plans for White
Against the isolated pawn, blockade d4 with a knight, exchange the pieces that support ...d4, and head for an ending. In the closed lines, defend d4 with c3, Ne2 and Nf3 and use the extra kingside space.
Plans for Black
In the Open System, keep pieces on and use them: ...Bd6, ...Ne7-f5, ...Bg4 and the e-file. In the closed lines, hit d4 with ...Nc6, ...Qb6 and ...cxd4, then use ...f6 to open the f-file.
For the wider picture, see the French Defense guide.