Main Line, Leonhardt Gambit

The Leonhardt Gambit, also called the Kotrč–Mieses Gambit, answers 3...Qa5 with 4. b4. The pawn offer deflects the queen while White develops with tempo, often aiming at c7 and f7. The name honors Paul Leonhardt, who introduced it against Jacques Mieses. Modern Chess Openings later credited the move to Jan Kotrč, although there is no record of him playing it. Lasker, Capablanca and Keres all used it. Engines consider the position roughly balanced, and with exact defense White's compensation may fall short, but in online games White scores well.

Black usually accepts with 4...Qxb4. White can then take the half-open file with 5. Rb1 Qd6 6. Nf3, gaining three developed pieces for the pawn. The sharper 5. Nb5 threatens Nxc7+. After 5...Qa5 6. Bc4, the natural 6...c6? fails to 7. Bxf7+ Kxf7 8. Qh5+ g6 9. Nd6+ exd6 10. Qxa5, when White wins the queen for two minor pieces. Declining with 4...Qb6 or 4...Qe5+ avoids these complications. Nigel Davies suggested delaying the push with 4. Nf3 Nf6 5. b4 Qxb4 6. a4, intending Ba3.