Chess Opening Theory/1. e4/1...c6/2. c4

With pawns on c4 and e4, White locks down d5 square. This is a rare, aggressive sideline against the Caro-Kann. It is "accelerated" over the regular Panov where White plays c4 only after 2. d4 d5 3. exd5 cxd5. This can lead to very different positions. A difference is that, in the accelerated Panov, White leaves their pawn on d2 until after they have castled, so they may place their knight on c3 without it becoming pinned.

2...d5, the main line, leads to a series of pawn trades: 3. cxd5 cxd5 4. exd5 Nf6 (4...Qxd5?! 5. Nc3! gains tempo on the queen). White is temporarily up a pawn but usually allows Black to take it back with 5. Nc3 Nxd5. In the resulting position, White is left with an isolated d-pawn. This is a weakness in an endgame, so it's important for White to capitalise on their middlegame chances, using the open lines created by the removal of their c- and e-pawns.

White can make a play to keep the extra material with the intermezzo 5. Bb5+, to force the knight or bishop to d7 and so obstruct Black's queen's defence of the pawn. However, this line usually results in a queen trade (5...Nbd7 6. Nc3 a6 7. Qa4 Rb8 8. Bxd7+ Qxd7 9. Qxd7+ Bxd7=) and in an endgame with doubled isolated d-pawns White may not feel the advantage of the extra material.

2...e5 is a sideline called the open variation. It's a bit like playing an open game (1. e4 e5), except now after 3. Nf3 Black can't defend the pawn with ...Nc6 because their pawn is misplaced on c6.

1.e4 c6 c4

Wikipedia has related information at Caro-Kann.

• Nunn's Chess Openings. 1999. John Nunn (Editor), Graham Burgess, John Emms, Joe Gallagher. ISBN 1-8574-4221-0.
• Modern Chess Openings: MCO-14. 1999. Nick de Firmian, Walter Korn. ISBN 0-8129-3084-3.
• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.