Chess Opening Theory/1. e4/1...e5/2. Nf3/2...f5/3. Nxe5/3...Qf6/4. Nc4

= Latvian Gambit, Leonhardt Variation =

4. Nc4
Black remains a pawn down, but White's knight has run off, so Black may now dream of playing …d5 in one move. That pawn on e4 will have to be cleared out of the way first, with /4...fxe4/. (If Black delays, White will play exf5 and retain the extra pawn.)