Chess Opening Theory/1. e4/1...c6/2. d4/2...d5/3. e5/3...Bf5

This is the main continuation to the advance variation. Black develops their bishop so that they may continue ...e6 to unleash their other bishop without restricting this one. The development of the bishop outside of the pawn chain is the key positional advantage difference between the Caro-Kann and the French.

White's choice here is between patient development and positional play, and attempting to capitalise on Black's bishop, which is unsupported and potentially vulnerable on f5.

White has the space advantage, now they just wish to get their pieces developed and surely they will have a good game.

The main line is 4. Nf3, the Short variation, 4...e6 5. Be2. White develops their kingside and prepares to answer ...c5 ...cxd4 with Nxd4. Once Black has played ...e6, their king's bishop supports the 5...c5 pawn break, though it is not forced and another idea^[1] is to develop their pieces before breaking on the kingside with ...f6.

Other moves include 4. Nd2, intending Nb3 and control of c5.

White has several ideas to harass it. In increasing order of audaciousness:

4. Nc3 is the sharp van der Wiel attack. White has a plan to harangue Black's bishop with g4 and h4-h5, and first includes Nc3 to take away the e4 square from the bishop. 4...e6 5. g4 Bg6 6. Nge2 c5 7. h4 (threatening 8. h5 winning the bishop) h5 8. Nf4 Bh7 9. Nxh5=; White wins a pawn but the line is sharp and offers Black good compensation.

4. h4, the Tal variation, is a more direct way of attacking Black's bishop. If 4...e6?? the bishop cannot be saved: 5. g4 Be4 6. f3 Bg6 7. h5±, showing that White doesn't have to include Nc3 if they're willing to play f3. 4...h6 provides an escape square but allows 5. g4 Be4 6. f3 Bh7 7. e6! Qd6 (if 7...fxe6?, Black has no hope of getting in the liberating ...e6 pawn move) 8. exf7+ Kxf7⩲. More common is 4...h5 5. Bd3 Bxd3 6. Qxd3 e6=.

4. g4!?, the Bayonet attack, is an even more direct way of attacking Black's bishop. In this order, 4...Be4 5. f3 Bg3 6. e6 (6. h4?! h5, White isn't in time to trap the bishop) Qd6 7. exf7+ Bxf7⩲. White has severely weakened their kingside before they've castled or developed any pieces, so was it really worth it?

4. Bd3?!, where White trades off Black's bad bishop for their good one, is considered inferior but a popular amateur try.

4. f4!?, White takes more space on the kingside before playing Nf3.

1.e4 c6 2.d4 d5 3.e5 Bf5

Wikipedia has related information at Caro-Kann.

• Schandorff, Lars (2010). The Caro-Kann. Quality Chess. ISBN 1906552568.