The Semi-Slav Defence can arise both from the Slav move order (1 Nf3 d5 2 d4 Nf6 3 c4 c6 4 Nc3 e6 or 1 Nf3 d5 2 d4 c6 3 c4 Nf6 4 Nc3 e6) and Queen’s Gambit Declined move order (1 Nf3 d5 2 d4 Nf6 3 c4 e6 4 Nc3 c6 or 1 Nf3 d5 2 d4 e6 3 c4 Nf6 4 Nc3 c6).
In contrast to the Slav, here Black gives up on developing his queen’s bishop directly by blocking it in with …e6. While this represents a concession, it does give White a problem in deciding how to continue, as Black is threatening to win a pawn by …dxc4 and …b5. White needs to decide whether to stop this or not.
The Botvinnik Variation and related systems
White’s sharpest approach is to play 5 Bg5, when he needs to be ready for:
- 5 …dxc4 (the Botvinnik Variation), when the critical line is 6 e4 b5 7 e5 h6 8 Bh4 g5 9 Nxg5 hxg5 10 Bxg5 Nbd7 followed by either 11 g3 or 11 exf6.
- 5 …h6 (the Moscow Variation), when the critical line is 6 Bh4 dxc4 7 e4 g5 8 Bg3 b5 9 Be2.
- 5 …Nbd7 6 e3 Qa5 (the Cambridge Springs Defence), when the critical line is 7 cxd5 Nxd5 8 Qd2 Bb4 9 Rc1 h6 10 Bh4 c5 11 a3 Bxc3 12 bxc3.
I have personally found this the most interesting and rewarding approach as White, although it requires good preparation, calculation and nerves.
I would refer the reader to the books by Khalifman, Cox and Schandorff mentioned above for more information on these lines.
The Meran Variation and related systems
A more restrained approach is introduced by 5 e3. Black normally replies 5 …Nbd7, when White has a choice between 6 Bd3 (the Meran) and 6 Qc2 (the Anti-Meran).
After 6 Bd3 the usual continuation is 6 …dxc4 7 Bxc4 b5 8 Bd3 Bb7. Now White’s main choices are:
- 9 e4 b4 10 Na4 c5 11 e5 Nd5 (the Wade Variation)
- 9 0-0 a6 10 e4 c5 11 d5 (the Reynolds Variation)
Both these lines lead to complicated play.
Beside these continuations, two dangerous sidelines worth considering for White are 9 a3 and 8 Be2.
White can attempt to sidestep the lines after 6 Bd3 with 6 Qc2, which discourages …dxc4 for the moment, since the move would lose a tempo. Black instead plays 6 …Bd6, when White has a variety of moves. The most aggressive choice is 7 g4, while 7 Be2, 7 Bd3 and 7 b3 all represent more measured approaches.
The various systems after 6 Qc2, and Black deviations on move 5, are covered in Sakaev and Semkov’s book “Latest Trends in the Semi-Slav: Anti-Meran”.