It seems like the main difference is whether the QB goes to b7 or f5. Is this correct? What sorts of positional differences does this lead to? is particularly active at one square?
For some reason I have the impression that the semi-slav is far more complicated and more theoretical, especially in the Botvinnik and Moscow variations. Is this true? if so, why?
Thanks
Black's QB is often a late bloomer in many other QP defenses besides the semi-slav, so deciding on either the Slav, Semi-Slav, or an "orthodox defense" to the QGD such as Lasker's Defense, Tartakower's Defense, Ragozins Defense etc is more a matter of taste and style than a matter of one defense being inferior or superior to another. (Note: I'm lumping all non-Slav QGD Openings together as "orthodox" defenses, although they are all seperate of the "Orthodox Defense" proper)
As usual, estragon has hit the nail on the head here and I learned something about the Slav and Semi-Slav Defenses just by reading his comments.
The main difference I see is that in the semi-slav, Black threatens to take on c4 (dxc4) and hang on to the pawn (with the typical complicated positions arising in the Botvinnik and Moscow Gambit variations).
Should white want to avoid this, he has to settle for the Meran variation (5.e3), which you could see as an improved QGD for Black, as white's Bc1 is much less agressively posted than in a regular QGD.
And yes, the Semi-Slav is much more complex than the regular Slav with dxc4...
I guess the thing that is bothering me is that I do not see why many of Black's plans in the semislav cannot also be played in the slav. Doesn't black threaten to hold the same pawn in the slav?
And conversely, why does white never play a4 in the semi-slav? How is this related to ...e6?
In the Slav after 4...dxc4, white plays 5.a4, and Black can't defend the c4 pawn with 5...b5 (6.axb5 cxb5 7.Nxb5 Qa5+ 8.Nc3 for example).
In the main line semi-slav, after 4...e6 5.Bg5 (5.e3 defends c4 of course) dxc4 6.a4, Black has the option 6...Bb4 (thanks to ...e6!) 7.e3 b5 when the c4 pawn is protected.
Ah, thanks hicetnunc(I think I finally got your name--Latin, right?)
so in the slav does Black normally not get much queenside play at all? What is his main plan?
http://www.chess.com/article/view/gelfandrsquos-harmless-looking-idea-vs-anandrsquos-meran
http://www.chess.com/article/view/larsenrsquos-improved-meran-the-great-dane-deigns-to-allow-check
http://www.chess.com/article/view/megatheory-1-semi-slav
http://www.chess.com/article/view/the-slav-by-gm-magesh-and-gm-arun
pellik explained it wonderfully : the dxc4 Slav is more of a waiting game, but your pieces have reasonable squares and your position is sound, if slightly passive. In contrast, the semi-slav is much more double-edged, if white accepts the complications of course...
Hello
I have been looking at both the slav and the semi-slav, and I do not understand why Black shuts in his QB with e6 in the semi-slav when the d-pawn is defended and cxd4 is threatened just as much without e6. e6 also means that Bg5 is a pin, which becomes very important in the semi slav botvinnik variation. What is the advantage of the semi slav?