Moves: 1. e4 c5
The moves 1. e4 c5 characterise the Sicilian Defence, a counter-attacking opening in which both players typically attack on opposite sides of the board. The Sicilian emerged into the mainstream in the early 20th century as a somewhat tame variation, but with the discovery of new attacking ideas it became Black's most feared weapon by the 1950s and is, pound for pound, the most exhaustively analysed of all openings. Black's move c5 seeks to half-open the c-file for his own use, controls the important d4 square and allows his queen to venture out if desired, while the itinerant c-pawn itself is safe from attack unlike the e-pawn after 1. e4 e5. It has the benefit of introducing an element of asymmetry into the position - White would not be advised to play 2. c4 imitating Black's move, since he could no longer control the d4 square with a pawn and thus will have trouble playing d4 later.
Faced with a pawn on c5, White may choose to play 2. d4 anyway which typically leads to a pawn sacrifice for quick development. A more usual and probably sounder idea is for White to postpone d4 for a move while he increases his own control of the square. This can be achieved by either 2. Nf3 leading to the main lines of the Sicilian, or by 2. c3, attempting to establish a strong pawn centre. Much less common is the attempt to undermine the c-pawn's control of d4 by playing 2. b4 to tempt it off-centre. Since it is considered safe for Black to take the offered pawn and hold on to it, a recent idea has been to prepare the b4 move with 2. a3.
White may postpone the fight for d4, typically with 2. Nc3 though 2. f4 is also played. 2. f4 is a violent attacking move, 2. Nc3 typically leads to a closed position although f4 can subsequently appear.
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