Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nc3/3...dxc4/4. e3/4...b5

Slav Defence D15 4...b5 This guards c4 and is the best move. The queenside weaknesses are not a problem, as the knight on c3 is vulnerable to b-pawn attacks with ...b4. Note that 5. Nxb5?, trying to exploit the long diagonal to destroy Black's queenside, is a mistake, and gives up the advantage to Black. A common motif in these positions is for Black to play b5 in order to boot the knight, often giving up the c4-pawn in the process. When your opponent has a space advantage, you want to use pawn breaks to break up their pawn chains. /5. a4/ is the most effective way to do that. The alternative 5. b3?! Qa5 results in Black being able to put a lot of pressure on White's queenside. Theory table 5. a4 b4 6. Ne4 Qd5 7. Nd2 c3 8. bxc3 bxc3 9. Nb1 Qa5 + 5. ... ... 6. ... ... 7. Ng3 Nf6 8. Be2 g6 9. Nf3 O-O 5. Nxb5? cxb5 6. Qf3 -- See also Slav Defence 3...dxc4