Chess Opening Theory/1. d4/1...d5/2. c4/2...e6/3. Nc3/3...Nf6/4. Nf3/4...c6/5. Bg5

=Semi-Slav Defence=

5.Bg5
This super-sharp move is often today a true gambit. White intends to offer the c-pawn as a real sacrifice. Here Black can try the solid 5...Nbd7, which leads into the Queen's Gambit Declined (Cambridge Springs Variation), the sharp Botvinnik Variation (5...dxc4 6.e4 b5 7.e5 h6 8.Bh4 g5 9.Nxg5! hxg5 10.Bxg5 with tremendous complications), or the even sharper main line, 5...h6 6.Bh4 dxc4 7.e4 g5 8.Bg3 b5.

Theory table
.

'''1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 e6 5. Bg5'''