In chess, one of the most solid and reliable defenses against White's most popular opening move, 1.e4 (1. P-K4). The Caro-Kann has been played at the highest levels of chess tournament and match play for many years now, and is generally favoured by the kind of player who prefers to play for equality, or a draw, with the black pieces, and only try to win matches with the advantage of the white pieces.
The first move of the Caro-Kann defense is 1...c6 (1...P-QB3), and depending on White's reply the game can take on various forms, but the basic idea for black is to establish a firm hold on the white squares in the centre (via the pawn push 2...d5 (2...P-Q4), to maintain a solid, almost unbreakable pawn structure, to develop pieces, and to establish equality via the eventual pawn push to c5 or e5 (P-QB4 or P-KB4).
The position after 1.e4 c6 2.d4 d5:
+----+----+----+----+----+----+----+----+
| r | n | b | q | k | b | n | r |
+----+----+----+----+----+----+----+----+
| p | p | | | p | p | p | p |
+----+----+----+----+----+----+----+----+
| | | p | | | | | |
+----+----+----+----+----+----+----+----+
| | | | p | | | | |
+----+----+----+----+----+----+----+----+
| | | | P | P | | | |
+----+----+----+----+----+----+----+----+
| | | | | | | | |
+----+----+----+----+----+----+----+----+
| P | P | P | | | P | P | P |
+----+----+----+----+----+----+----+----+
| R | N | B | Q | K | B | N | R |
+----+----+----+----+----+----+----+----+
Similar ideas are found in the French Defense which begins 1.e4 e6 2.d4 d5, but a major difference is that in the Caro-Kann Black is not locking in the light-squared bishop, which often develops to the f5 square. This bishop is a well-known problem in the French. The disadvantage when compared to the French is that 1...c6 is not really a developing move, and so White has a slightly easier time building up an ideal piece formation in the center.
White's main alternatives from the diagram above are:
- 3.e5 - the Advance Variation, claiming more space in the center and keeping the position closed. This is not as effective a plan as it is in the French Defense, since Black can now play 3...Bf5 followed by 4...e6 with a good game based on pushing the c6-pawn to c5 to undermine White's center. However there are some sharp attacking lines for White and both players need to be prepared well.
- 3.exd5 cxd5 4.Bd3 - the Exchange Variation, uninspired but very solid. Practically anything equalizes for Black, but both sides may find it difficult to win.
- 3.exd5 cxd5 4.c4 - the Panov-Botvinnik Attack, a very sharp and popular opening that transforms the solid character of the Caro-Kann and deserves its own writeup.
- 3.Nc3 (or 3.Nd2) - this is the main line, and the most logical move, developing a piece and protecting the e4 pawn at the same time. Black invariably replies 3...dxe4 when after 4.Nxe4 Black has a further choice of 4...Nd7, 4...Nf6 and 4...Bf5, all of which have been through reams of analysis and thousands of grandmaster games. 4...Bf5 is the main line, while 4...Nd7 was popularised by the late Tigran Petrosian and 4...Nf6, once thought dubious, was revitalized by Bent Larsen.
Notable Caro-Kann players have included Anatoly Karpov, Viktor Korchnoi, Tigran Petrosian and Vassily Smyslov, but the majority of the world's top players have tried it at some time or another.
Thanks to Miles_Dirac for prodding me into improving this writeup!