Slav Defense

The Slav Defense meets the Queen's Gambit by defending d5 with the c-pawn instead of the e-pawn. Compared with 2...e6 in the Queen's Gambit Declined, the queen's bishop is not shut in, and Black avoids the pawn structure that invites a minority attack in the Exchange QGD. If Black later captures on c4, the c6-pawn supports ...b5, either to keep the pawn or to gain time against a piece that recaptures it. There are costs. The bishop often cannot come out until Black has given up the center with ...dxc4, its departure can leave the queenside loose, and the ...c5 break costs a tempo. The Slav is separated from the related Semi-Slav by avoiding or postponing ...e6, although the two often transpose.

At move three White chooses among 3. Nf3, the Modern Line and the traditional main move, and 3. Nc3, which is the most frequent reply in the database. After 3. Nc3 the immediate ...Bf5 fails to cxd5 and Qb3, and 3...dxc4 is a more attractive option than it is against 3. Nf3. 3. cxd5 is the Exchange Variation. Its symmetrical structure and open c-file make it a well-known drawing line, and Black sometimes reaches the Semi-Slav by another move order to avoid it. 3. e4, the Diemer Gambit, is a rare sideline.

The central position arises after 3. Nf3 Nf6 4. Nc3, where Black has four main options. 4...dxc4 is the "pure" Slav. Its principal line, 5. a4 Bf5, is the Czech Variation: a4 stops ...b5 and prepares e4 with Bxc4, and the bishop on f5 prevents e4. White's sharpest alternative is the Geller Gambit, 5. e4 b5, a pawn sacrifice whose soundness remains disputed. 4...a6, the Chebanenko Variation, became popular in the 1990s. It prepares ...b5 without blocking the bishop or giving up the center. White can respond 5. c5 to gain queenside space, after which ...e5 and ...b6 become Black's main breaks. 4...e6 transposes to the Semi-Slav, and 4...g6, the Schlechter Variation, is much rarer. White can avoid the main-line theory with 4. e3, the Quiet Variation, which was tested in the 2006 World Championship.

The opening was analyzed as early as 1590, and Steinitz played it in his 1886 title match, but systematic study began only in the 1920s. Alapin, Alekhine, Bogoljubov and Vidmar did much to develop it, and the two Alekhine–Euwe World Championship matches of 1935 and 1937 tested it extensively. Euwe, Botvinnik and Smyslov favored it, and later Anand, Ivanchuk, Short and Kramnik adopted it. Kramnik used it in six of his eight Black games in the 2006 World Championship. Engines rate the starting position as close to balanced. In online play draws are rare and White scores somewhat better.