Chess Opening Theory/1. e4/1...c5/2. Nf3/2...d6/3. d4/3...cxd4/4. Nxd4

= Open Sicilian =

White's knight removes Black's d-pawn, freeing their f-pawn to advance, and radiates power in all directions from its central post.

The resulting exchanges have left White with a semi-open d-file and Black with a semi-open c-file. White has also swapped a central pawn for a wing pawn. According to Fred Reinfeld, if a center (d- or e-) pawn is worth about $1.00, a bishop's (c- or f-) pawn is worth about $0.90. Therefore, Black has, in effect, swapped a dollar for a dollar, but kept the ten cents as change! Fortunately, to compensate for this, White has a marked spatial advantage in the center, plus a small lead in development. Using their open d-file, White will attempt to pressure Black's d6-point. In some lines, Black voluntarily makes this pawn on d6 backward with the advance ...e7-e5 in exchange for dynamic play in the center and queenside. While it is true that Black does not always achieve this play in the center, they almost always get queenside play rolling with ...a7-a6 and ...b7-b5. If White castles queenside, these pawns will be a dangerous attacking force. However, if White castles kingside, the danger posed by these pawns is significantly less, although they are still part of a positional plan to expand on the queenside.

White has a pawn on the fourth rank. Nominally, it gains space, and many battles have been fought over whether this space advantage is relevant. However, in many variations of the Sicilian (particularly the Najdorf Variation), the e-pawn becomes a target. This can also be seen in the natural development of Black's pieces: ...b7-b5, ...Ng8-f6, and sometimes ...Nb8-d7-c5. When the neighboring pawn on f2 advances to the fourth rank, White gains more space on the kingside, getting good chances for attack there. In all, this adds up to a very sharp game, which is why the Sicilian Defence is the most popular opening today.

Theory table
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'''1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4'''