King's Gambit, Classical Variation

Classical Variation

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Moves	1.e4 e5 2.f4 exf4 3.Nf3 g5
ECO	C37-C39
Parent	King's Gambit

The Classical Variation of the King's Gambit is a chess opening that begins with the moves:

1. e4 e5

2. f4 exf4

3. Nf3 g5

By playing this move, Black supports the pawn on f4, aiming to prevent it from being recaptured after d4 and Bxf4 from White. The move also threatens to kick the f3-knight with ...g4, or else to consolidate with ...Bg7 and ...h6. White's most common reply is 4.h4, most often continuing 4...g4 5.Ne5, the Kieseritzky Gambit. The next most common is 4.Bc4, most often continuing 4...Bg7, the Traditional Defense, or 4...g4 5.0-0, entering the Muzio Gambit. Also somewhat common are the Rosentreter Gambit, 4.d4, and the Quaade Gambit, 4.Nc3.

3...g5 was the main line of the King's Gambit in the 19th century and remains the most common today, although it is no longer as dominant. After Bobby Fischer lost to Boris Spassky in a 1960 game in the Kieseritzky Gambit, Fischer developed and advocated the alternative 3...d6 in a famous 1961 article in the first issue of the American Chess Quarterly.^[1][2] Both lines are well regarded.

In the Encyclopaedia of Chess Openings, the Classical Variation is given the codes C37 through C39.

The line has been studied since at least the 1500s. The main line, now known as the Kieseritzky Gambit, was first described by Polerio in the late 16th century. Greco also included a game with this opening in his 1620 collection.^[3] It was also analyzed by Salvio (1604) and Philidor (1749).^[4]

This move practically forces 4...g4. Attempting to create a pawn chain loses the advantage due to 4...h6 5.hxg5 hxg5 6.Rxh8 (or 4...f6 5.Nxg5 fxg5 6.Qh5+ Ke7), so Black instead counterattacks, forcing White to move the knight, most commonly to e5, the Kieseritzky Gambit.

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Kieseritzky Gambit

The Kieseritzky Gambit, 4.h4 g4 5.Ne5, is considered by modern writers such as Shaw and Gallagher to be the main line after 3...g5. It was popularized by Lionel Kieseritzky in the 1840s and used successfully by Wilhelm Steinitz. Boris Spassky used it to beat Bobby Fischer in a famous game at Mar del Plata in 1960.^[5] Black's most common response is 5...Nf6, the Berlin Defense. The main line of the gambit continues 6.Bc4 d5 7.exd5 Bd6, also known as the Anderssen Defense. Play most often continues 8.d4, followed by 8...Nh5 or 8...0-0. If White instead plays 8.0-0, this leads to the Rice Gambit.

White also commonly plays 6.d4, the Rubinstein Variation, which usually continues 6...d6 7.Nd3 Nxe4 8.Bxf4. White may also play 6.Nxg4, inviting the surprising forcing continuation 6...Nxe4 7.d3 Ng3 8.Bxf4 Nxh1 (8...Qe7+ 9.Be2 is also common and escapes the sequence) 9.Qe2+ Qe7 10.Nf6+ Kd8 11.Bxc7+ Kxc7 12.Nd5+ Kd8 13.Nxe7 Bxe7, leading to an extremely imbalanced position where White has a rook, bishop, and knight in exchange for Black's queen and one pawn.

A common alternative to 5...Nf6 is the Kolisch Defense, 5...d6 6.Nxg4. It commonly continues with 6...Nf6 7.Nxf6+ (or 7.Nf2) Qxf6, returning the gambited pawn in exchange for quick development, or with 6...Be7 7.d4 Bxh4+ 8.Nf2 Bg3, remaining up a pawn but granting White the initiative. The Long Whip Variation, 5...h5?! 6.Bc4 Rh7 (or 6...Nh6), is also common but is considered old-fashioned and risky, as Black loses a lot of time attempting to hold on to the pawn.

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Allgaier Gambit

4.h4 g4 5.Ng5 is the Allgaier Gambit,^[6] planning 5...h6 (5...d5 is an alternative) 6.Nxf7 Kxf7. The sacrifice of the knight leads to sharp positions with attacking chances but is considered unsound.^[7] It may also be reached by transposition from the Fischer Defense, though this is uncommon, with White usually responding to ...g4 with Ng1 rather than Ng5.

Play usually continues according to White's plan with 5...h6 6.Nxf7 Kxf7. After this, lines include the Horny Defense, 7.Qxg4 Nf6 8.Qxf4 Bd6; the Thorold Variation, 7.d4; the Cook Variation, 7.d4 d5 8.Bxf4 dxe4 9.Bc4+ Kg7 10.Be5+; the Blackburne Gambit, 7.Nc3; and the Urusov Attack, 7.Bc4+, which often continues 7...d5 8.Bxd5+ Kg7 9.d4. An alternative fifth move for Black is the Schlechter Defense, 5...Nf6.

• 4...d5 the only accurate alternative to 4...g4. Despite this, it is rarely seen.
• 5.Ng1 is rare but playable.

This move most often indicates the intention to play the Muzio^[8] Gambit, which is the best regarded line for White after 4...g4. It has the advantage of reinforcing White's attack along the f-file.

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Muzio Gambit, 5.O-O

The extremely sharp Muzio Gambit arises after 4.Bc4 g4 5.0-0 gxf3 6.Qxf3, where White has sacrificed a knight but has three pieces bearing down on f7.^[9] Such wild play is rare in modern chess, but Black must defend accurately, usually responding with 6...Qf6 or 6...Qe7.

What is potentially the sharpest continuation is the Double Muzio, which is reached after 6...Qf6 7.e5 Qxe5 8.Bxf7+!?, leaving White two pieces down in eight moves, but with a position that some masters consider to be equal,^[10][11] and quite difficult for Black to defend against without preparation.

An alternative to 5...gxf3 is 5...d5 (the Brentano Defense). It typically continues with 6.exd5 gxf3 7.Qxf3 Bd6 8.d4 Ne7 (or 8...Qf6). 5...Qe7?! (the Kling and Horwitz Counterattack) is another option but poorly regarded. It usually continues 6.d4 gxf3. White must play 7.Nc3 to capitalize, intending 8.Nd5. 7.Qxf3 transposes to the main line.

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Salvio Gambit, Main Line, 5.Ne5 Qh4+ 6.Kf1

The Salvio Gambit, 5.Ne5, usually continues 5...Qh4+ 6.Kf1. It is rarely seen today, as it is considered better for Black due to the insecurity of White's king. However, White is threatening to inflict the same on Black with Bxf7+, supported by the knight on e5. Black commonly plays 6...Nh6 (the Silberschmidt Variation), attempting to address this, although the move is no longer well regarded. The main continuations are 7.d4 f3 (the Silberschmidt Gambit) and 7.d4 d6 8.Nd3 (the Anderssen Counterattack). Better regarded sixth moves for Black are an immediate 6...f3 (the Cochrane Gambit), 6...Nc6 (the Viennese Variation or Herzfeld Gambit), and 6...Nf6 (the Santa Maria Defense).

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Hanstein Gambit, 5.0-0 d6 6.d4 h6

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Philidor Gambit, 5.h4 h6 6.d4 d6

A common and safer alternative to 4...g4 is 4...Bg7,^[10] known as the Traditional Defense, which is often used as a method for Black to avoid the Muzio Gambit. It usually leads to the Hanstein Gambit after 5.d4 d6 6.0-0 h6 or 5.0-0 d6 6.d4 h6, the Philidor Gambit after 5.h4 h6 6.d4 d6, or the Mayet Gambit after 5.d4 d6 6.c3. Other move orders are possible in all cases, including via the Fischer Defense. If White plays 7.Qd3 in the Philidor Gambit, this is known as the Schultz Variation. Another alternative for Black is 4...Nc6, known as the Blachly Gambit.

• After 4.Bc4 g4, alternative but less common fifth moves for White are the Ghulam Kassim Gambit, 5.d4, and the McDonnell Gambit, 5.Nc3. Another line is 5.Bxf7+?!, the Lolli Gambit, also known as the Wild Muzio Gambit. It is considered to leave White with insufficient compensation for the piece after 5...Kxf7 6.Ne5+ Ke8 7.Qxg4 Nf6 8.Qxf4 d6.
• Fourth move alternatives for Black after 4.Bc4 such as 4...Nc6 and 4...h6 are also playable and commonly lead to transpositions to other lines. 4...d6, trying to transpose to either the Philidor Gambit with 5.d4 Bg7 6.h4 h6 or the Hanstein Gambit with 5.d4 Bg7 6.0-0 h6, is refuted by 5.h4! g4 (or 5...h6 6.hxg5, as 6...hxg5?? would allow 7.Rxh8) 6.Ng5 Nh6 7.d4 and Black's f4-pawn will fall, leaving White with a superior position.

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Quaade Gambit, 4.Nc3 Bg7 5.d4 g4 6.Bxf4 gxf3 7.Qxf3

The Quaade^[12] Gambit (3.Nf3 g5 4.Nc3) is named after a Danish amateur who discussed it in correspondence with the Deutsche Schachzeitung in the 1880s.^[13] The move received renewed attention following its recommendation by John Shaw in his 2013 book on the King's Gambit, as a less explored alternative to 4.h4 and superior to 4.Bc4.^[14]

A well-known trap is 4...g4 5.Ne5 Qh4+ 6.g3 fxg3 7.Qxg4 g2+? (7...Qxg4 8.Nxg4 d5 is about equal) 8.Qxh4 gxh1=Q 9.Qh5! and White is close to winning. Black's best try is considered 9...Nh6 10.d4 d6 11.Bxh6 dxe5 12.Qxe5+ Be6 13.Qxh8 Nd7 14.Bxf8 0-0-0, but White is a clear pawn ahead. Because of this, after 4.Nc3 g4 5.Ne5, Black is considered better off playing 5...d5 rather than 5...Qh4+.

4...Bg7 is a more common alternative move for Black that has been recommended. White's most common reply is 5.d4, followed by 6.g3. After 5.d4 g4, Simon Williams advocates 6.Bxf4 gxf3 7.Qxf3.^[15] White is down a knight, but has a strong attack. Black more commonly plays 5...d6 instead, transposing to the Fischer Defense, or 5...h6, transposing to the Becker Defense. These transpositions can also occur on the fourth move. Another possible fourth move for Black is 4...Nc6, recommended by Konstantin Sakaev,^[16][17] which transposes to the Vienna Game.

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Sørensen Gambit, 4.d4 g4 5.Ne5 Qh4+ 6.g3 fxg3 7.Qxg4 g2+ 8.Qxh4 gxh1=Q

The Rosentreter Gambit (3.Nf3 g5 4.d4) often leads to positions similar to those of the Quaade Gambit, or transposes to it, but with some notable distinctions. For example, both lines allow the forcing line 4...g4 5.Ne5 Qh4+ 6.g3 fxg3 7.Qxg4. In the Rosentreter Gambit, where this line is known as the Sørensen Gambit, Black achieves better results than in the Quaade Gambit. After 7...Qxg4 8.Nxg4, in the Quaade, White has the threat of 9.Nd5, which would fork Black's king and rook after 10.Nxc7+. In the Rosentreter, this is not available.

Alternatively, after 7...g2+ 8.Qxh4 gxh1=Q, in the Quaade, this leads to the mentioned trap with 9.Qh5. In the Rosentreter, 9.Qh5 is not possible due to 9...Qxe4+. White most often continues with 9.Nc3 (Shaw's recommendation^[18]), leading to a complicated but relatively equal position. A delayed version of White's attack from the Quaade will not succeed due to 9...Nc6 10.Qh5 Nxe5 11.Qxe5 Ne7 (or 11...Be7), but White can regain the sacrificed rook, either immediately with 12.Qxh8, or with 12.Bg5, where it can be retaken at a later time.

The most common fourth move alternatives for Black are 4...Bg7, typically transposing to the lines of the Quaade Gambit discussed earlier, 4...d6, transposing to the Fischer Defense, and 4...h6, transposing to the Becker Defense.

• 4.h3 is rare but playable.

• List of chess openings

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