Originally considered a less-orthodox defence in the Queen's Gambit, this opening has stood as an entire opening system in its own right for decades.

The idea behind this defence is straightforward: instead of locking in the light squared bishop on c8, why not support the center with the c-pawn instead? Black tends to be more active in this variation than the QGD.

White's main lines:

• 3. Nf3 - The main line. As with the QGD, white makes a useful developing move while maintaining some flexibility: will they play for e4, play cxd5, or play for the minority attack?
• 3. Nc3 - Sometimes provocative, this move may lead to variations where black overextends by trying to hold on to the pawn on c4.
• 3. cxd5 - The exchange variation. This relieves the central tension perhaps too early on and tends to allow black equality. One of the main drawbacks of having the Slav as a main opening repertoire is that it is hard for Black (or White) to win in the exchange variation. According to chess365, 83% of Masters games ended in a draw after this move. Even so, it is important for both sides to know that there are still attacking options to sharpen up the game.

For explanation of theory tables, see theory table and for notation, see algebraic notation..

1. d4 d5 2. c4 c6

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.