King's Gambit Accepted: Kieseritzky Gambit

The Kieseritzky Gambit is 1.e4 e5 2.f4 exf4 3.Nf3 g5 4.h4 g4 5.Ne5, the main line of the Classical Variation of the King's Gambit and one of its main lines overall. Black tries to protect the f4-pawn with ...g5, White undermines the pawn chain at once with 4.h4, and Black has little choice but 4...g4. The knight then jumps to e5. The overall verdict is still unclear but roughly equal. Its ECO code is C39.

Origins

Polerio described the opening in the late 16th century, Greco included a game with it in his 1620 collection, and Salvio (1604) and Philidor (1749) analysed it. In the first edition of the Handbuch in 1843, 5.Ne5 was still treated under the Allgaier Gambit, but the editors noted that Kieseritzky had contributed much to its theory and preferred it to 5.Ng5, an opinion almost every later analyst has shared. The second edition in 1852 had a chapter headed "Allgaier and Kieseritzky's Gambit", and afterwards the name Kieseritzky Gambit came into general use for 5.Ne5.

In 1960 Boris Spassky used it to beat Bobby Fischer, which led Fischer to develop the Fischer Defense, 3...d6.

The alternative 5.Ng5, the Allgaier Gambit, sacrifices the knight after 5...h6 6.Nxf7 Kxf7 and is considered dubious.

Main lines

• 5...Nf6, the Berlin Defense, is the most common reply: it attacks the weak e4-pawn and controls central squares. White answers 6.Bc4, 6.Nxg4 or 6.d4. After 6.Bc4 d5 7.exd5 Bd6 8.d4 Nh5, the Anderssen Defense and the main line of the whole gambit, 9.O-O Qxh4 10.Qe1 Qxe1 11.Rxe1 is roughly equal. 6.Nxg4 is relatively drawish.
• 5...d6, the Kolisch Defense, is the main sound alternative. After 6.Nxg4 Nf6 7.Nxf6+ Qxf6 Black returns the pawn for quick development.
• 5...h5, the Long Whip, was once considered a critical test but is now regarded as dubious: Black holds the pawn at the cost of a large lead in development and attacking chances for White, who usually replies 6.Bc4.
• Other fifth moves for Black include 5...d5, the Brentano Defense, 5...Qe7, the Salvio Defense, 5...Bg7, the Paulsen Defense, and 5...Nc6, the Neumann Defense. Against most of them White's best reply is 6.d4.

Who should play it

The Kieseritzky is for King's Gambit players who want the classical main line with 3.Nf3 and are ready for sharp, well-analysed positions. Black has several sound answers, so White needs to know the theory.

The numbers

On Lichess White wins 50.4% of the 440,000 games and Black 46.1%, and the split hardly moves with rating: 51.5% against 45.8% under 1400, and 48.3% against 46.8% from 2200 up. In 421 master games over the board Black did better: Black won 34.0%, White 23.8%, and 42.3% were drawn.