Main Line

The Main Line of the Semi-Slav Defense is the position after 5. e3. Here it arises through the order 3. Nc3 Nf6 4. e3 e6 5. Nf3. Supporting c4 with a pawn removes Black's threat of ...dxc4 and ...b5, and the play stays quieter than after 5. Bg5. The price is that White's queen's bishop stays shut in behind the e3 pawn for the time being. White usually continues with Bd3 and aims for e3-e4. Black looks to capture on c4 at a suitable moment and free the position with ...c5 or ...e5.

The engine's preferred reply is 5...Nbd7, the Normal Variation. After 6. Bd3 dxc4 7. Bxc4 b5 it reaches the Meran, and White can also choose one of the Anti-Meran systems instead. 5...a6, sometimes called the Accelerated Meran, is regarded as a solid option. On Lichess the most frequent reply is 5...Be7, but it is rare in master play because the bishop stands passively on e7 and does not support ...e5. 5...Bd6 is also common online. White scores slightly better in Lichess games, and the engine rates the position as roughly balanced.