1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 g6 is called Sicillian dragon opening. This is less popular than Sicilian Najdorf, but still very popular at all levels of chess. Black wants to fianchetto the bishop and castle short instead of playing e5 or e6 and Be7.
White has two major ways of playing against the Sicilian dragon.
Yugoslav attack with 6.Be3
The most dangerous for black is the Yugoslav attack. This may be the reason that most players are discouraged from playing the dragon altogether. 6.Be3 Bg7 7.f3 0-0 8.Qd2 Nc6 is the main variation of Yugoslav attack.
White intends to castle long and create a strong kingside attack with g4-h4-h5-Bh6.
Just a side note that black can’t discourage 6.Be3 with 6…Ng4??, which turns out to be a blunder.
White wins material after 7.Bb5+. 7…Bd7 and the g4 knight falls with 8.Qxg4!
Continuing the main line, white has two options on move 9.
White plays 9.Bc4
The idea of move 9.Bc4 is to stop the break d5.
The main line goes 9…Bd7 10.0-0-0 Rc8 11.Bb3 Ne5 12. h4 Nc4 13.Bxc4 Rxc4 14.h5 and although the game is objectively equal, white has a dangerous potential for attack.
Black cannot allow white’s h pawn to live any longer. Black must play 14…Nxh5 and after 15.g4 Nf6 16.Bh6 Nxe4 17.Qe3 black can play a typical Sicilian exchange sacrifice with 17…Rxc3 18.bxc3 Nf6 and the game is dynamically equal.
Soltis variation with 12…h5
Instead of counter attacking directly with Nc4, black can slow down white’s attack with 12…h5 first. It is called the Soltis variation.
The game can go 13.Bg5 Rc5 14.Kb1 b5 15.g4 a5 16.gxh5 Nxh5 17.Nd5
As you can see, white has mounted up the attack but black has also set-up a good potential for counter attack. Black’s plan will be to play Re8, defend the e pawn and then Nc4-a4 and try to create a counter attack.
White plays 9.0-0-0
Instead of 9.Bc4, white can play 9.0-0-0.
It is important to note the difference here. Black can’t continue with the same plan of Ne5-c4, because it will give white too many extra tempos after Bf1xc4. But what has white left behind by not playing Bc4? The d5 square.
Therefore black’s standard move should be immediate 9…d5. After 10.Kb1, black can’t take on e4 because of 11.Nxc6 Qxd2 12.Nxe7+ and white wins a piece.
The main line goes 10…Nxd4 11.e5 Nf5 12.exf6 with a very sharp game!
Black can go 12…exf6 13.Bc5 Re8 or also dare a queen sacrifice with 12…Bxf6 13.Nxd5 Qxd5 14.Qxd5 Nxe3 15.Qd3 Nxd1 16.Qxd1
Black gets a bishop and a rook for the queen with two dangerous bishops and an initiative for attack.
Classical variation with 6.Be2
Back then, white’s other alternative is to play quiet game with 6.Be2. The idea is to castle short and play in the spirit of Najdorf.
The main line goes 6…Bg7 7.0-0 0-0 8.Be3 Nc6 9.Nb3 Be6 10.f4 trying to increase pressure on the center.
Here, black can play 10…Na5, with the idea of Nc4. There is also an interesting idea with 10…Qc8. The move controls the g4 square with the idea to play Ng4 and also frees up the d8 square for the rook.
After 11.Kh1 Rd8 12.Bg1 d5 13.e5 Ne4 14.Bd3 black has two ways of playing.
14…Nxc3 15.bxc3 Bf5 16.Nxd4 Bxd4 with an equal game.
White has doubled pawns on c-file but they are not weak. In fact, white has a good center control and open b file to occupy.
Better for black is 14…f6, undermining white’s center as soon as possible.
Conclusion
The sicilian dragon is very popular and sharp opening. But it gives white opportunity to play the dangerous Yugoslav attack. Black has to be well prepared with the study of detailed theory of this variation. White can also opt for the classical variation and try to gain more of the center. The game then takes more of a positional style.