Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nf3/3...Nf6/4. e3

White plays the quiet move 4. e3, introducing more positional play as white is yet to commit the b1-knight to c3. As such, the position remains flexible for both sides and a variety of openings can occur.

Black's most common responses are 4...Bf5 and 4...e6, with the latter frequently transposing back into a mainline Semi-Slav defence. However, White can avoid such a Semi-Slav transposition on move 5 with a variety of options, such as Bd3, b3, Nbd2, and Qc2 rather than Nc3. Other responses from Black include 4...a6, 4...g6, and 4...Bg4, all of which are frequently played.

White tends to score similarly in this quiet variation compared to the mainline Slav variations.

1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. e3