 The idea is to prepare b2-b4 by white, which would make it more difficult for black to achieve his strategic plan of pushing c6-c5.Black may respond with moves like 9...b4, 9...Bd6, 9...a6 or 9...a5.Intent of the move 8...Bd6 is to allow rapid castling as well as to increase black's control over the e5-square, which will be critical in many continuations.