Kyle,

I was merely suggesting that Black has to know what to do against 3.d5.  Because it is so rare, White would probably get a nice advantage against anyone who is unfamiliar with the move.  As I stated, it's interesting.  But I would probably develop a piece rather than push the pawn, too.

In other words, you're exactly right that theoretically, it shouldn't be a big deal.  I'll try to respond more fully in the near future.

BTW:  One problem of reaching the Semi-Slav via 1...Nf6 could be move order.  For instance:

A:  1.d4 Nf6 2.c4 d5?! (?) is probably just bad for Black.

B:  1.d4 Nf6 2.c4 c6!? allows 3.d5!? which is probably good for White, but at least it's interesting.

C:  1.d4 Nf6 2.c4 e6 (the best and most obvious move for trying to transpose into the Semi-Slav without playing 1...d5) allows White to play a number of good moves that may throw off your opening plans.  White could play 3.Nc3 or 3.Nf3 which wouldn't be a problem for Black.

But White could also play 3.g3 (the Catalan) or 3.Bg5 which would eliminate the Meran from your list of options.  But since White can avoid the Meran most of the time anyway...

In other words, as is usual in chess, avoiding certain lines by playing slightly unusual move orders runs the risk of playing into other lines that you may not be ready to meet at all.

Ad 2) Yes. White's gambit idea usually is to allow b7-b5 and occupy the centre with e2-e4 at once. Then play will have some similarities with ...g5 lines of the KG Accepted.

Ad 4) In case you play the Caro-Kann (I have forgotten), why not 1...c6 ?

Hello,

The Meran is a particular variation of the semi-slav, first played by Rubinstein, at least in top level chess, in 20's or probably earlier. (The line mentioned by Inn2 and others, with a6, intending quick c5. Nowdays, Bb7 (Wade variation) is more common, but can transpose to same positions.)

Bye John S

There are several lines in the Slav where Black gets the oppoturnity for the greedy dxc4 and b5 trying to get an extra pawn. White can play an early e3 to protect his c4 pawn, even as early as move 3. But i think this is rather wet, White should develop both his knights ASAP and not be afraid to gambit his c4 pawn for the initiaive. A White 1. d4  player who doesn't learn to play like this is like a 1. e4 player who never learned how to play the Open Sicilian.

Some definitions:
Semi-Slav Meran: 1.d4 d5 2.c4 c6 3.Nc3 Nf6 4.Nf3 e6 5. e3 Nbd7 6.Bd3 (6. Qc2- Karpov) dc4 (6... Bd6 is a playable alternative) 7.Bc4 b5
Semi-Slav Botvinnik: 1.d4 d5 2.c4 c6 3.Nc3 Nf6 4.Nf3 e6 5. Bg5 dxc4
Semi-Slav Moscow: 1.d4 d5 2.c4 c6 3.Nc3 Nf6 4.Nf3 e6 5. Bg5 h6 6. Bxf6 (6. Bh4! dxc4 7. e4 g5 8. Bg3 b5- Anti-Moscow Gambit, pretty strong for White imho)
Main Slav:  1.d4 d5 2.c4 c6 3.Nc3 Nf6 4.Nf3 dxc4, 5. e4 here is dubious, so the main line is 5. a4 Bf5 6. Ne5! or 6. e3.
<"Triangle System">
Noteboom: 1.d4 d5 2.c4 c6 3.Nc3 e6 4. Nf3 dxc4
Slav Marshall Gambit: 1.d4 d5 2.c4 c6 3.Nc3 e6 4. e4
Anti-Noteboom Systems: 1.d4 d5 2.c4 c6 3. Nf3 e6 4. Qc2 (or 4. Bg5!?)

The choice between 3. Nc3 and 3. Nf3 is primarily for White to decide how he wants to meet the "triangle system". The Slav Marshall is theoretically the most dangerous for Black. But 3. Nc3 allows additional deviations like 3... e5!?? (Winawer Countergambit) and 3... dxc4 (this is less strong in the case of 3. Nf3 since b5-b4 does not gain a tempo on 3. Nc3),  i think these deviations should not be feared though, so 3. Nc3 is the strongest move on the board. But many GMs do not like complications, so they start with 3. Nf3 instead, intending to squeeze a small edge against the "triangle" with 3. Nf3 e6 4. Qc2.

Pardon my ignorance,  but whats the diff? They both look very similar to me esp the c6 move. Meran & semi-slav the same??

Most common 3rd move by white is 3.ktf3. Why? Isnt 3.Ktc3 'sharper'?

I suppose they are the sharpest QGDs at black's disposal?

Any overview wld be greatly appreciated. thanks.