411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...c6/2. d4/2...d5/3. Nc3/3...dxe4/4. Nxe4/4...Bf5/5. Bd3
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Classical variation B18 Caro-Kann → Classical variation
5. Bd3?!
White develops a piece and gives up defence of the d4-pawn, allowing 5...Qxd4, in return for the compensation of getting to develop 6. Nf3 with tempo.
References