King's Gambit Declined: Falkbeer Countergambit, Anderssen Attack

The King's Gambit Declined: Falkbeer Countergambit, Anderssen Attack is a chess opening classified under ECO code C31 in the Open Games & French Defense family, beginning with 1.e4 e5 or 1.e4 e6, including the Italian Game, Ruy Lopez, and French Defense. It is reached after 4 moves: 1. e4 e5 2. f4 d5 3. exd5 e4 4. Bb5+. The resulting position leaves black to move.