Sicilian Defense: O'Kelly Variation, Réti System

The Sicilian Defense: O'Kelly Variation, Réti System is a chess opening classified under ECO code B28 in the Semi-Open Games family, where Black responds to 1.e4 with something other than 1...e5, including the Sicilian Defense, Caro-Kann, and Pirc. It is reached after 3 moves: 1. e4 c5 2. Nf3 a6 3. g3. The resulting position leaves black to move.