Understanding The Semi-Slav Defense D43

1.d4 d5 2.c4 e6

The Semi-Slav is a relatively recent addition to Black's queen pawn defenses. It was originated by Alapin a century ago and came into prominence during the 1935-37 World Championship matches between Alekhine and Euwe. It has remained popular since, and today it is used by several young Russian stars, although its leading exponent is Anand, who is virtually invincible with it.

The positions that arise in this Semi-Slav are among the strategically richest in all of chess. Deep calculations are also required, as there are some very long forcing variations.
Black haa a simple idea capture the pawn at c4 and hold on to it by advancing the b-pawn to b5. The bishop at c8 can find a home at b7, and an eventual ...c5 will give it powerful scope on the long diagonal.
White can choose to preserve the pawn with 5.c3, at the cost of shutting in the bishop at c1, or allowing Black to carry out the plan, receiving in return an ideal pawn center after advancing the pawn at e2 to e4. Both approaches have advaocates at the higheest level of chess and hundreds of pages of analysis have been devoted to each path. This is due to the complexity of the positions, which can feature such obscure items as four queens on the board (two for each side) and coutrageous pawn structures. Both tactical prowess and positional ability are required to solve the puzzles that lie in virtually every position.
The sharpest lines are often found in the sacrifice of the c-pawn.

Basic Semi-Slave Defense

Botvinnik Attack
Mikhail Botvinnik was not afraid of complications, and it is only fitting that this complicated variation bears his name. Although the tableau is peaceful, for the moment, there is molten lava just beneath the surface. It usually explodes volcanically after Black captures the pawn at c4 and White creates the ideal pawn center with e4, Black then holds on to the pawn with b5, and White responds by smashing open the kingside with a piece sacrifice!
Lots of fun for all, but the accumulation of theory has created a massive amount of work for anyone who wants to master its complexities.
Botvinnik Attack

Stoltz Variatio
The idea behind the Stoltz Variation is to battle for control of the e4 square and also to set up threats against h7 should Black castle short, as is customary in the Semi-Slav. This variation rested in obscurity for several decades before exploding onto the tournament scene in the mid-1980's. It has now become one of the main lines of the Semi-Slave but Black's defenses are holding up and it may soon submerge again.
Stoltz Variation

Wade Varuation
The Wade Variation was named after British Theoretician Bob Wade. The most popular move is 9.e4, but the position takes on more individual character after 9.a3, which has been rising in popularity. The bishop on f8 is not hiding. It is ready to take part in the action after and eventual c5.
Wade Variation

Meran Variation: Main Line
In the normal handling of the Meran Variation, Black will play a6 rather than Bb7. In this way, the c-pawn can advance more quickly. Time is of the essence, since White is about to build the ideal pawn center with e4. Black has a number of weaknesses on the queenside, but if the minor pieces are well coordinated, than everything can be held together. If White is not careful, Black will take advantage of a queenside pawn majority created when the c-pawn reaches c4.
Meran Variation

The Games

Nikolic - Kramnic

Gelfand - Kramnik

Burn - Telchmann

Fahmi -Swiderski

Tolush - Bronstein

Beilin - Kamishov

Fuster - Gereben

Herink - Sefc

Stehlik - Niederwieser

Vaulin - Korotylev