Alekhine Defense: Four Pawns Attack, Cambridge Gambit

The Alekhine Defense: Four Pawns Attack, Cambridge Gambit is a chess opening classified under ECO code B03 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 5 moves: 1. e4 Nf6 2. e5 Nd5 3. d4 d6 4. c4 Nb6 5. f4 g5. The resulting position leaves white to move.