Chess Opening Theory/1. d4/1...d5/2. c4/2...c6/3. Nf3/3...Nf6/4. Nc3/4...dxc4

Black finally takes the sacrificial pawn with dxc4. Despite being known as the "Pure Slav," this move has about half the popularity of 4...e6, the Semi-Slav. The idea of this move is to threaten a pawn advance onto White's queenside. White can choose to either allow the queenside expansion and gambit the c-pawn, or they can prevent it and give Black time to develop the light-squared bishop.

White can prevent Black's pawn advance by playing 5. a4, known as the Alapin variation. This move directly stops 5...b5 but gives Black valuable tempi while White is trying to regain the pawn. Nonetheless, this is White's most promising option and thus considered to be the main line, with many branches to follow.

Instead of spending valuable tempi to regain the pawn, White can opt to gambit the pawn in exchange for a development advantage. This can be done in multiple ways.

5. e4, the Slav gambit (also known as the Geller gambit) is the most popular way to achieve this. White takes over the center while Black expands on the queenside. While the main line of this variation has been studied by many players and is even considered to be good for Black, there is still some venom in more unexplored continuations.

5. e3 is less ambitious than 5. e4, but keeps White's center more stable. Known as the Alekhine variation, White tries to provoke Black to over-extend their queenside pawns and chip them away later.

Some rarer moves include 5. g3, prioritizing development over central expansion, and 5. Ne5, going for g3, Bg2 and generating tension on the a8-h1 diagonal.

1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 dxc4

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