Philidor Defense: Nimzowitsch Variation, Klein Variation

The Philidor Defense: Nimzowitsch Variation, Klein Variation is a chess opening classified under ECO code C41 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. Nf3 d6 3. d4 Nf6 4. Bc4. The resulting position leaves black to move.