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 a later d4 and Bxf4 from White. The move also threatens to kick White's knight on f3 with ...g4, or else to consolidate with ...Bg7 and ...h6. However, the move also weakens Black's kingside. White's most common reply is 4.h4, most often continuing 4...g4 5.Ne5, the Kieseritzky Gambit, the main line of the variation. 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]

White's most common move in response to 3...g5 is 4.h4, which all but 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. Black can also play 4...d5, but this is rare.

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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,^[6] the Berlin Defense. The main line of the gambit continues 6.Bc4 d5 7.exd5 Bd6, also known as the Anderssen Defense.

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.

The main sound alternative to 5...Nf6 is the Kolisch Defense, 5...d6 6.Nxg4.^[6] 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.

There are other playable alternatives, such as 5...d5, 5...Qe7, 5...Nc6, 5...Bg7, and most notably 5...h5?!, which is known as The Long Whip Variation. It typically continues 6.Bc4 Rh7 (or 6...Nh6), but it 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,^[7] 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.^[8] 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.

• White can also play 5.Ng1, similarly to the main line of the Fischer Defense, but this is rare.

The move 4.Bc4 most often indicates the intention to play the Muzio^[9] Gambit, which Black can accept with 4...g4 and 5...Nxf3. This allows a powerful attack from White along the half-open f-file, pressuring Black's isolated pawn on f4, or Black can decline to play into White's plan with 4...Bg7.

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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.^[10] 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,^[11][12] 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).

This most often continues 5...gxf3 6.Qxf3, leading to a position similar to the Muzio Gambit. White can also play 6.0-0, where the move 6...fxg2 is weak due to 7.Bxf7+ Kxf7 8.Rxf4+.

After 6.Qxf3, common replies for Black include 6...d6 and 6...d5, defending the square g4, which otherwise may be used for later attacks from White's queen after Bxf7+ sacrifices.

• After 4.Bc4 g4, alternative but less common fifth moves for White are 5.d4, the Ghulam Kassim Gambit, and 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.

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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,^[11] known as the Traditional Defense, which is often used as a method for Black to avoid the Muzio Gambit. White usually responds with 5.d4, usually transposing to another line; 5.0-0, the Hanstein Gambit; or 5.h4, the Philidor Gambit. Other move orders are possible in all cases, including via the Fischer Defense.

The main line continues 5.0-0 d6 6.d4 h6. It can also be reached from 5.d4 via 5...d6 6.0-0 h6 or 5...h6 6.0-0 d6.

The main line is 5.h4 h6 6.d4 d6. It can also be reached from 5.d4 via 5...d6 6.h4 h6 or 5...h6 6.h4 d6. The move 7.Qd3 is known as the Schultz Variation.

• After 5.d4 d6, another possibility for White is the Mayet Gambit, 6.c3.

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

The Quaade^[13] Gambit (3.Nf3 g5 4.Nc3) is named after a Danish amateur who discussed it in correspondence with the Deutsche Schachzeitung in the 1880s.^[14] 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.^[15]

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.^[16] 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,^[17][18] 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^[19]), 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.

• Fourth move alternatives for Black after 4.Bc4 such as 4...Nc6 (known as the Blachly Gambit) and 4...h6 are also playable and often end up transposing 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.
• After 4.h4, 4...d5 is the only sound alternative. Possible continuations include 5.Nxg5 h6 5.Nh3 dxe4, 5.d4 dxe4 6.Nxg5 Nf6, and 5.exd5 g4 6.Ne5 (or 5...Qe7+ 6.Kf2).
• 4.h3 is rare but playable.

• List of chess openings

The Wikibook Chess Opening Theory has a page on the topic of: Classical Variation