ECO D18: Slav Defense

ECO D18 is part of volume D — Closed & Semi-Closed Games. The Lichess chess-openings dataset files 2 named lines under it. The shortest is Slav Defense: Czech Variation, Classical System: 1. d4 d5 2. c4 c6 3. Nf3 Nf6 4. Nc3 dxc4 5. a4 Bf5 6. e3.

That position has come up in 326,272 Lichess games between players rated 1600 to 2500: White won 45.9%, 7.7% were drawn and Black won 46.3%.