Semi-Slav Defense

The Semi-Slav Defense is a variation of the Queen's Gambit Declined chess opening defined by the position reached after the moves:

The position may readily be reached by a number of different move orders. Black's supporting pawns resemble a mixture of the Orthodox Queen's Gambit Declined, e6, and the Slav Defense, c6.

Black is threatening to capture the white pawn on c4 and hold it with ...b7–b5. White can avoid this in a number of ways. About 80% of games continue 5.Bg5 or 5.e3: the former constitutes a sharp pawn sacrifice, while the latter restricts the dark-squared bishop from its natural development to g5. Other possible moves are 5.Qb3, 5.g3 and 5.cxd5, the last of which, after 5...exd5, leads to a line of the QGD Exchange Variation where White's early Nf3 enables Black's queen bishop to freely develop, which should give equality (ECO codes D43 and D45). 5.Bf4 is considered somewhat inaccurate, as 5...dxc4 is favorable for Black.

The Semi-Slav is designated by codes D43 through D49 in Encyclopaedia of Chess Openings.

It is possible to reach the Semi-Slav through many move orders. White may start the game with either 1.d4, 1.Nf3 or even 1.c4, keeping the possibility of a Semi-Slav open. Black can choose different combinations of ...d5, ...c6, ...e6 and ...Nf6 as well in order to avoid certain variations or to open up some new opportunities of his own. This chapter looks at the first moves of the game from Black's point of view, assuming that he would prefer to play the Semi-Slav.

If White opens the game with 1.d4, Black is happy to respond with 1...d5 when aiming for a Semi-Slav. Of course, White can continue the game with 2.Bf4 or even 2.Bg5 (as is the case if Black opens 1...Nf6), and the game will take a completely different path. In the vast majority of master games, however, White players choose to play either 2.c4 (Queens Gambit) or 2.Nf3. After 2.Nf3, the natural continuation for Black is 2...Nf6. Playing 2...c6 or 2...e6 might be somewhat inaccurate, since White always has the option of avoiding c2–c4, so developing the knight first makes a lot of sense.

If White chooses the most common 2.c4, Black has three practical choices: either protect the pawn on d5 by playing e6 or c6 (keeping the option of a Semi-Slav open), or alternatively capture the white pawn with dxc4 (leading to Queen's Gambit Accepted). The first thing for Black players to consider is, what if White captures on d5 anyhow with cxd5. If Black has played the Slav move order (2...c6), then after the recapture cxd5 ("exchange Slav") the pawn structure is symmetrical. Should Black have played 2...e6 instead, the recapture exd5 leads to an imbalanced pawn structure called the Carlsbad structure, which might offer White some opportunities for a minority attack on the queenside.

Protecting the d5-pawn with the c-pawn has at least three implications for Black. First, it allows Black to keep the option to enter the Slav Defense, i.e., developing his light-squared bishop to f5 at the appropriate moment, before moving his e-pawn. Second, it may discourage White from capturing on d5, given the somewhat drawish reputation of the Exchange Slav. Third, it prevents White from entering the Catalan opening with 3.g3.