Chess Opening Theory/1. e4/1...c6/2. d4/2...d5/3. Nc3/3...dxe4/4. Nxe4

4. Nxe4 is an obvious recapture. This is the traditional treatment of the Caro-Kann and may arise from either the 3. Nc3 or 3. Nd2 variations.

Black has three main alternatives.

4...Bf5 is the classical variation. The bishop ends up controlling the long diagonal first from g6 via the manoeuvre 5. Ng3 Bg6, then from h7 after 6. h4 h6 7. Nf3 Nd7 8. h5 Bh7.

4...Nf6, developing the knight instead, leads to 5. Nxf6+ exf6, the Tartakower variation. This is perfectly playable but Black has to accept doubling their pawns.

4...Nd7 is the Smyslov or Karpov variation. This looks slower, as the knight will have to move again before the light-square bishop can enter the game. If Black ends up trading their knight on f6, they may recapture with another knight rather than double their pawns: 5. Nf3 Ngf6 6. Nxf6 Nxf6. Otherwise, the main move is 5. Ng5.

None of the other alternatives have seen significant usage. 4...h6 is known as the Finnish variation.

Wikipedia has related information at Caro-Kann.

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