comment: This is played in order to prevent White from developing the bishop on f4.
context: 1. e2e4  1... c7c6  2. d2d4  2... d7d5  3. e4d5  3... c6d5  4. f1d3  4... b8c6  5. c2c3 This variation against the Caro-Kann Defense is more poisonous than it seems. Bobby Fischer achieved a famous and devastating victory against Tigran Petrosian using this line.