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.)

Wikipedia has related information at Latvian Gambit.

• Nunn's Chess Openings. 1999. John Nunn (Editor), Graham Burgess, John Emms, Joe Gallagher. ISBN 1-8574-4221-0.

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.