Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nc3/3...dxc4/4. e3/4...b5/5. Nxb5

Slav Defence
a b c d e f g h 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 a b c d e f g h
Position in Forsyth-Edwards Notation (FEN) rnbqkbnr/p3pppp/2p5/1N6/2pP4/4P3/PP3PPP/R1BQKBNR b
Moves: 1. d4 d5 2. c4 c6 3. Nc3 dxc4 4. e3 b5 5. Nxb5

5.Nxb5?

This clever attempt to win material is a huge mistake, and gives black two ways to get an advantage, the first one being the best. In one way, the queen will get trapped on a8, and black will build a cage and try to win the queen. Black can also return the piece, with a lead in development and huge queenside space advantage.

a4 is better, when b4 Ne4 Qd5 is the normal continuation and white will try to rip black's space-gaining queenside to bits. Black would try to strengthen it.

Theory table

5	6	7	8
Nxb5 cxb5	Qf3 Qc7	Qxa8 Bb7	Qxa7 e5!	-/+
	Qf3 Nc6	Qxc6+ Bd7	Qf3 e5!	-/=