Schliemann Defence and Jaenisch Gambit

The Schliemann ‘s Defence or Schliemann–Jaenisch Gambit, 3…f5!?, is a sharp line in the Ruy Lopez and occurs after the moves

1.e4 e5 2.Nf3 Nc6 3.Bb5 f5

Black plays for a kingside attack, frequently sacrificing one or two pawns. Considered by many to be somewhat dubious, it is occasionally used in top-level play as a surprise weapon. This variation was originated by Carl Jaenisch in 1847 and is sometimes named after him. Although later named for German lawyer Adolph Karl Wilhelm Schliemann (1817–72), the line Schliemann actually played in the 1860s was a gambit variation of the Cordel defence (3…Bc5 4.c3 f5). The most common responses for White to 3…f5!? are 4.d3 or 4.Nc3, with play after 4.Nc3 fxe4 5.Nxe4 going 5…d5, with great complications to follow, or 5…Nf6, which generally leads to quieter play.

You can find more Openings by Schliemann in ‘Search Openings‘