Halloween Gambit

The Halloween Gambit, also called the Müller–Schulze or Leipzig Gambit, gives up a knight for the e5 pawn. In return White builds a broad center and drives back Black's knights with gain of time. Black almost always takes with 4...Nxe5, and after 5. d4 the knight retreats to g6 or c6. After 5...Ng6 6. e5 Ng8 White develops with 7. Bc4, and 7...Bb4 8. Qf3 f5 is the Oldtimer Variation. The 5...Nc6 retreat is met by 6. d5. In the main line, 6...Ne5 7. f4 Ng6 8. e5 Ng8 9. d6 cxd6 10. exd6, the threat of Nb5-c7 makes White's attack dangerous in practice, and 10...Qf6 11. Nb5 Rb8 is the Plasma Variation. Larry Kaufman considered the gambit refuted by Jan Piński's 5...Nc6 6. d5 Bb4 7. dxc6 Nxe4 8. Qd4 Qe7.

Engines give Black a large advantage, and the line is uncommon in tournament chess. Even so, White scores well in online games, where unprepared defenders often go wrong. Oskar Cordel reported in 1888 that Leipzig club players used it effectively, though he doubted it was sound. Steffen Jakob, who revived it in the 1990s, gave it its modern name.