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

Slav Defence
	a b c d e f g h 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 a b c d e f g h
	Position in Forsyth-Edwards Notation (FEN) rnbqkbnr/p3pppp/2p5/1p6/2pP4/2N1P3/PP3PPP/R1BQKBNR
	Moves: 1. d4 d5 2. c4 c6 3. Nc3 dxc4 4. e3 b5
	ECO code: 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

1. d4 d5 2. c4 c6 3. Nc3 dxc4 4. e3 b5

5	6	7	8	9
a4 b4	Ne4 Qd5	Nd2 c3	bxc3 bxc3	Nb1 Qa5	⩲
... ...	... ...	Ng3 Nf6	Be2 g6	Nf3 O-O	=
Nxb5? cxb5	Qf3				∓

4...b5

Theory table

See also