Chess Opening Theory/1. d4/1...d5/2. c4/2...e6/3. Nc3/3...c6/4. Nf3/4...dxc4

With this move Black enters the aggressive Noteboom variation.

White can attempt to win back the pawn like in the Alapin Slav with 5. a4 but Black can take advantage of that move with 5...Bb4. After 6. e3, attacking the pawn, Black can defend it with 6...b5, making use of the fact that after 7. axb5 cxb5 White's knight on c3 is still pinned and can't capture the pawn on b5.

White's other option is to try to win back the pawn with the immediate 5. e3 but Black will respond with 5...b5, defending the pawn. After 6. a4 Black has successfully provoked White into weakening the b4-square, where Black will once again place the dark-squared bishop, transposing into the previous line.

White can also choose to avoid the Noteboom with either 5. Bg5 the anti-Noteboom variation or with 5. g3 the anti-Noteboom gambit.

This opening was named after the player Daniël Noteboom, who played it in the 1930 Chess Olympiad.^[1]

1. d4 d5 2. c4 e6 3. Nc3 c6 4. Nf3 dxc4

Wikipedia has related information at Semi-Slav Defence.