1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 e5 is the Sveshnikov Sicillian. This is also a very popular variation of Sicilian defense. By playing 5…e5, black allows a hole d5 square in his position. But on the other hand he gains a few tempo by kicking the white knight.
After 6.Ndb5 d6 7.Bg5 a6 8.Na3 b5 we reach the main position of the Sicilian Sveshnikov.
Black is threatening b4. White has to move his c3 knight to d5. There are two main options in this position. White can play 9.Nd5 right away or he can choose 9.Bxf6 first, and then play Nd5.
White plays 9.Bxf6
The idea of 9.Bxf6 is to give black doubled pawns on f file and clear the d5 square for white knight right away.
It is natural to take with the queen here, but it turns out to be a mistake.
After 9…Qxf6 10.Nd5, white is threatening Nc7+. The queen has to go back to 10…Qd8 and after 11.c4, white gets a better position.
In Sicilian defense, every move counts. Here, black wasted two moves by Qxf6 and Qd8 and it costs a lot. The b5 pawn is attacked and black has no good way of defending it. 11…bxc4 12.Nxc4 gives white a wonderful position.
After 11…b4, white has 12.Qa4!, a nice in-between move winning material. After 12…bxa3 13.Qxc6+ Bd7 14.Qxa8! Qxa8 15.Nc7+ and white wins a rook.
And if 12…Bd7, then 13.Nb5! Rc8 14.Qxa6, and white wins material.
So black must play 9…gxf6. And the main line goes 10.Nd5 f5 11.c3 and here black cannot capture the e4 pawn.
11…fxe4 12.Bxb5! axb5 13.Nxb5 and white threatens the dangerous Nbc7+ not only forking the a8 rook, but also threatening checkmate.
For example, careless 13…Rb8 loses immediately to 14.Nbc7+ Kd7 15.Qg4+ f5 16.Qxf5#.
So the main line is 11…Bg7 12.exf5 Bxf5 13.Nc2 0-0 14.Nce3 and we reach a dynamic position.
Black has two bishops but white has a strong outpost d5 in the center. White is yet to spare two moves to finish the development. Black can play 14…Bg6 or 14…Be6 with ideas of f5-e4. The game is objectively equal, but very sharp.
White plays 9.Nd5
By playing 9.Nd5, white gives up the opportunity to give black doubled pawns and settles for a quiet play. The main line goes 9…Be7 10.Bxf6 Bxf6 11.c3 0-0 12.Nc2 Bg5 13.a4 bxa4 14.Rxa4
White has given black a weak pawn on a-file. Black will try to counter in the center with his two bishops and f pawn.
A sample game can go 14…a5 15.Bc4 Rb8 16.b3 Kh8 17.0-0 f5 18.exf5 Bxf5 19.Nce3 Bg6 with equal position.
Conclusion
Sveshnikov Sicilian is a good opening for black to play. But one must be aware of sharp tactics and sacrifices which are possible on the b5 square. By playing a6-b5 too early, black risks falling into tactics. But on the other hand gains initiative and two bishops advantage for long term.
