Knights Gambit variations

King's Knight's Gambit: 3.Nf3
Classical Variation: 3...g5
The Classical Variation arises after 3.Nf3 g5. Black defends his extra pawn, and threatens to kick the f3-knight with ...g4.

Becker Defense: 3...h6
The Becker Defense (3.Nf3 h6), has the idea of creating a pawn chain on h6, g5, f4 to defend the f4 pawn while avoiding the Kieseritzky Gambit, so Black will not be forced to play ...g4 when White plays to undermine the chain with h4. White has the option of 4.b3, although the main line continues with 4.d4 g5 (ECO C37) and usually transposes to lines of the Classical Variation after 5.Bc4 Bg7 6.0-0 (ECO C38).

Bonch–Osmolovsky Defense: 3...Ne7
The rarely seen Bonch–Osmolovsky Defense (3.Nf3 Ne7) was played by Mark Bluvshtein to defeat former world title finalist Nigel Short at Montreal 2007, even though it has never been highly regarded by theory.

Cunningham Defense: 3...Be7

The Cunningham Defense (3.Nf3 Be7) threatens a check on h4 that can permanently prevent White from castling; furthermore, if White does not develop his King's Bishop immediately, he would be forced to play Ke2, which hems the Bishop in. A sample line is 4. Nc3 Bh4+ 5. Ke2 d5 6. Nxd5 Nf6 7. Nxf6+ Qxf6 8. d4 Bg4 9. Qd2. White has strong central control with pawns on d4 and e4, while Black is relying on the white king's discomfort to compensate.

To avoid having to play Ke2, 4. Bc4 is White's most popular Black can play ...Bh4+ anyway, forcing 5.Kf1 (or else the wild Bertin Gambit or Three Pawns' Gambit, 5.g3 fxg3 6.0-0 gxh2+ 7.Kh1, played in the nineteenth century). In modern practice, it is more common for Black to simply develop instead with 4...Nf6 5.e5 Ng4, known as the Modern Cunningham.

Schallopp Defense: 3...Nf6

The Schallopp Defense (3.Nf3 Nf6) – intending 4.e5 Nh5, holding onto the pawn – is considered somewhat inferior[citation needed] and is rarely played today. In one of the lines, White can usually obtain a crushing attack via a rook sacrifice, 4.e5 Nh5 5.d4 g5 6.h4 g4 7.Ng5 Ng3 8.Bc4! Nxh1 9.Bxf7+ Ke7 10.Nc3 (looking for immediate mate at d5, or later via queen at f6) and Black appears doomed.

Modern Defense: 3...d5
The Modern Defense, or Abbazia Defense, (3.Nf3 d5) has much the same idea as the Falkbeer Counter-Gambit, and can in fact be reached by transposition, e.g. 2.f4 d5 3.exd5 exf4. Black concentrates on gaining piece play and fighting for the initiative rather than keeping the extra pawn. It has been recommended by several publications as an easy way to equalize, although White keeps a slight advantage due to his extra central pawn and piece activity. If White captures (4.exd5) then Black may play 4...Nf6 or recapture with 4...Qxd5, at which point it becomes the Scandinavian Variation of KGA.

Fischer Defense: 3...d6
Main article: King's Gambit, Fischer Defense
"The refutation of any gambit begins with accepting it. In my opinion the King's Gambit is busted. It loses by force." – R. Fischer, "A Bust to the King's Gambit"

The Fischer Defense (3.Nf3 d6), although previously known, was advocated by Bobby Fischer after he was defeated by Boris Spassky in a Kieseritzky Gambit at the 1960 Mar del Plata tournament. Fischer then decided to refute the King's Gambit, and the next year the American Chess Quarterly published Fischer's analysis of 3...d6, which he called "a high-class waiting move".

MacLeod Defense: 3...Nc6
Joe Gallagher writes that 3.Nf3 Nc6 "has never really caught on, probably because it does nothing to address Black's immediate problems." Like Fischer's Defense, it is a waiting move. An obvious drawback is that the Nc6 may prove a target for the d-pawn later in the opening.

Wagenbach Defense: 3...h5
An invention of the Hungarian/English player, János Wagenbach. John Shaw writes: "If given the time, Black intends to seal up the kingside with ...h4 followed by ...g5, securing the extra pawn on f4 without allowing an undermining h2–h4. The drawback is of course the amount of time required".