The Slav Defense
The Slav Defense is a chess opening that begins with the moves:
The Slav is one of the primary defenses to the Queen's Gambit. Although it was analyzed as early as 1590, it was not until the 1920s that it started to be explored extensively. Many masters of Slavic descent helped develop the theory of this opening, including Alapin, Alekhine, Bogoljubov, and Vidmar.
The Slav received an exhaustive test during the two Alekhine–Euwe World Championship matches in 1935 and 1937. Played by 11 of the first 13 world champions, this defense was particularly favored by Euwe, Botvinnik, and Smyslov. More recently the Slav has been adopted by Anand, Ivanchuk, Lautier, Short, and other top grandmasters, including use in six of the eight games that Vladimir Kramnik played as Black in the 2006 World Championship (in the other two, he played the related Semi-Slav Defense).
Today the theory of the Slav is very extensive and well-developed.
The Slav Defense with 4.Nc3 a6 and gambit lines after 4. Nc3 dxc4
The one with 1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.Bf4
D12: Slav Defence: 3.Nf3 Nf6 4.e3 Bf5
D10: Slav Defense with 3.Nc3 Nf6 4.Bg5