Semi-Slav Defense

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This article uses algebraic notation to describe chess moves.

The Semi-Slav Defense is a variation of the Queen's Gambit chess opening, defined by the opening moves 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Nf3 c6, although the moves are not always played in that order. The opening resembles a mixture of the Orthodox Queen's Gambit Declined and the Slav Defense.

With 4...c6 Black is threatening to take the white pawn on c4, and keep it with a ...b5 advance. White can hold on to the pawn with 5.e3 at the cost of blocking the dark-squared bishop. Alternatively, White often gambits a pawn with 5.Bg5, the Anti-Meran Gambit, which Black may accept with 5...dxc4 6.e4 b5, leading to sharp play, or decline with 5...h6, the Moscow Variation. If Black plays the latter variation, White can play 6.Bxf6 Qxf6, ceding the bishop pair in exchange for a lead in development, or again offer a gambit with 6.Bh4!? The Encyclopaedia of Chess Openings designates the Semi-Slav with codes D43 to D49.

[edit] Main Variations

• The main variation of the Semi-Slav is the Meran Variation, 5.e3 Nbd7 6.Bd3 dxc4, (ECO codes D46 to D49), when play usually continues with 7.Bxc4 b5 8.Bd3. Black surrendered the centre for a moment, but won a tempo because the white bishop moved twice, first to d3 then to c4. Black then made a grab for queenside space and initiative by playing ...b5. White will play in the center, Black will aim to get a powerful initiative on the queenside often leading to a tense, sharp and complicated game.

• The Anti-Meran Gambit (ECO code D44) comes after 5.Bg5. This line is also extremely complicated. White refuses to shut in the dark-squared bishop, instead developing it to an active square where it pins the black knight, but Black can now win a pawn by 5...dxc4. White takes charge of the centre with 6.e4 and Black proceeds to defend his booty with 6...b5. Usually the game now continues with 7.e5 h6 8.Bh4 g5 9.Nxg5 hxg5 10.Bxg5 Nbd7. White will get his piece back, along with two pawns, meaning he will be a pawn up, but Black will soon complete his development while White will be lagging behind. This is frequently referred to as the Botvinnik System. White will fianchetto his king's bishop and castle kingside, while black will play ...c5, ...Qb6, castle long, and can carry an attack on either flank leading to absurdly complex play. The opening was popularized by the 1949 USSR vs USA radio match Arnold Denker vs Mikhail Botvinnik. Today, Alex Yermolinsky has an excellent record with the White pieces and Alexei Shirov champions the Black pieces in this opening.

• Another increasingly common gambit to the Meran system is 6.Qc2 Bd6 7.g4! Popularized by Alexander Shabalov, the gambit destabilizes the center for Black and has been successful for several grandmasters, including Kasparov. It has also been successful against computers, in games such as Kasparov vs. Deep Junior, Game 1.

• The Moscow Variation 5.Bg5 h6 6.Bxf6 Qxf6, leads to double-edged play. Black has the bishop pair, but must avoid allowing White to open the game too quickly and exploit Black's lagging development. The gambit line 6.Bh4 (the Anti-Moscow Variation) was once considered rather dubious, but has seen a recent resurgence. In return for the gambited pawn, White receives a lead in development and a strong initiative. This dynamic mode of play, which is characteristic of the modern game has seen this line being played by many strong grandmasters.

• Calmer lines can be found in the remaining ECO codes, D43 and D45. If White wants to avoid the Meran Variation without entering the muddy waters of the Anti-Meran gambit, 5.cxd5 or 5.Qb3 are possibilities. Alternatively, after 5.e3 Nbd7, a popular alternative to 6.Bd3 is 6.Qc2, effectively waiting for black to commit to dxc4 before playing Bd3.