Chess Opening Theory/1. e4/1...e6/2. d4/2...d5/3. Nc3/3...Bb4

Black immediately seizes the occasion to get rid of the white knight. An exchange is almost inevitable. By pinning the knight, the e-pawn is left unprotected.

White can put his pawn out of danger with 4. e5, which is considered to be the main line of the Winawer.

It should be noted that the dark-squared bishop is Black's "good bishop," as the light-squared bishop is stuck behind the pawn chain. The exchange however does give Black some compensation after the usual 4. e5 c5 5. a3 Bxc3 6. bxc3 as the closed position is quite solid for Black and their superior queenside is more agile than White's jammed centre. However after the usual and flexible 6...Ne7 White can choose between the tactical and very complex poisoned pawn variation (7. Qg4) or the strategic and complex lines following either a4 or Nf3. Play can be very difficult with lots of good chances for both players.

Apart from pushing the pawn forward, White has many alternatives for either protecting or gambiting the pawn.

4. exd5 turns the position into an exchange variation with Nc3 and ...Bb4 interposed. The addition of these two moves does create a more imbalanced position, making this variation somewhat less prone to drawn positions, unlike the original exchange variation.

4. Ne2 is the Alekhine-Maróczy gambit. White gambits the e4-pawn for a lead in development, intending to force Bxc3 with a3 and recapturing with the knight. White has an easier time developing their pieces while Black tries to fend off their attack.

4. Bd3 is popular at the amateur level, protecting the pawn with the bishop. This move isn't played much at the grandmaster level since Black enjoys fairly simple equality after 4...dxe4 5. Bxe4 Nf6 6. Bf3 O-O with e5 and/or c5 incoming.

4. a3 forces Black to exchange the bishop and intends to harass the kingside, which has now been weakened due to the missing bishop, with Qg4.

1. e4 e6 2. d4 d5 3. Nc3 Bb4

Wikipedia has related information at French Defence.

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.