The traditional move order for reaching the Semi-Slav is 1 d4 d5 2 c4 c6 3 Nf3 Nf6 4 Nc3 e6. In this order, Black initially keeps open the option of developing his queen’s bishop to f5 or g4. If he can do this safely, then he will have a comfortable position.
In the main line, where White plays 3 Nf3 and 4 Nc3, it is not advisable to play 4…Bf5, in light of 5 cxd5 cxd5 6 Qb3, while 4…Bg4 is met by 5 Ne5. Black therefore needs either to prepare the development of the bishop via 4…dxc4 or 4…a6, or choose another approach. In this series we will be looking at the main other approach, the Semi-Slav, which is introduced by 4…e6. The reasoning behind this move will be examined in a later post. What I think is important to remember here is that Black should look to develop his bishop actively if at all possible.
White’s main 4th move alternative is 4 e3. While this rules out 4…dxc4, it does allow Black to develop his bishop in a straightforward manner with 4…Bf5. The system 5 Nc3 e6 6 Nh4 requires decent preparation by Black, as it has been played at the top level, but his position remains solid.
On move 3, White has a tricky move order in the form of 3 Nc3. This poses a difficulty for anyone who plays 1 d4 d5 2 c4 c6 3 Nf3 Nf6 4 Nc3 dxc4, as White’s idea is to side-step this with 3…Nf6 4 e3. Then 4…dxc4 wastes time, while 4…Bf5 5 cxd5 cxd5 6 Qb3 causes Black problems. However, the move order is no problem for the Semi-Slav player, who just continues (after 3 Nc3 Nf6 4 e3) with 4…e6, and White will most likely play 5 Nf3, with one of the two main lines of the Semi-Slav.
White can play the Exchange Variation via several moves orders: 3 cxd5, 3 Nc3 Nf6 4 cxd5 and 3 Nf3 Nf6 4 cxd5. The traditional form of the Exchange involves White developing knights to c3 and f3; there is also a version where White plays Nc3, but delays the development of his other knight, with the intention of placing it on e2.
In addition to these major options, White also has a range of less popular lines on moves 4 and 4. For instance, as well as 3 Nf3, 3 Nc3 and 3 cxd5, White has also sometimes played 3 e3. On move four, White can defend the pawn on c4 with 4 Qc2, 4 Qb3 or 4 Nbd2, or continue with 4 g3. None of these are especially critical, but Black does need to have a clear plan of development in mind.
On move 2, if White plays 2 Nf3, Black should play 2…Nf6. Then 3 c4 c6 transposes back to the main line, while 3 e3 Bf5, 3 Bf4 c5 and 3 Bg5 Ne4 are all fine for Black.
White plays 1 c4
The response to 1 c4 that is consistent with the above system is 1…c6.
The lines 2 d4 d5, 2 Nc3 d5 3 d4 Nf6 and 2 Nf3 d5 3 d4 Nf6 all transpose to systems covered above.
2 e4 d5 transposes to the Pseudo-Panov Variation of the Caro-Kann. This can lead to the Panov proper after 3 exd5 cxd5 4 d4, or to independent lines if White refrains from d4.
If White holds back both d4 and e4, play usually leads into the Reti Opening. Black will then look to develop his bishop on f5 or g4, with a solid game.
White plays 1 Nf3
Black can meet 1 Nf3 with 1…d5, when 2 d4 Nf6 transposes to the lines covered after 1 d4, while 2 c4 c6 transposes to the lines covered after 1 c4.
Should White continue with 2 g3 or 2 b3, Black can develop solidly, looking to develop his bishop on f5 or g4. If White plays c4, play will lead to the Reti Opening than can also be reached via 1 c4.