King's Gambit

White attacks Black's pawn on e5 with the f-pawn, even though that pawn is itself attacked and undefended. White seeks to pry Black's pawn away from control of d4, so that they may place their own pawn there. In addition, White's trying to open the f-file so that once they have castled, their rook is activated on the open file immediately.

The king's gambit is a very aggressive opening that comes with severe trade offs. By moving the f-pawn so early, before they have castled, White has greatly weakened their kingside and exposed their king to danger.

2...exf4, accepting the gambit, is the main move. Black grabs the extra pawn. Accepting the gambit and forcing White to justify an advantage is the most testing response. Although White has succeeded in deflecting the pawn, they cannot play 3. d4?! yet because Black threatens 3...Qh4+!.

Usually White controls h4 first with 3. Nf3, sometimes called the king's knight gambit. This leads to a variety of continuations that promise Black a superior position. In most lines, Black will try to hold on to the pawn with ...g5 and exploit the e1-h4 and a7-g1 diagonals with ...Qh4+ and ...Bc5.

3. Bc4, the bishop's gambit, is an alternative: White allows 3...Qh4+ intending Kf1 & Nf3 to gain tempo on the queen. The usual move is 3...Nf6, although 3...d5 and 3...Nc6 have their merits.

There are several effective ways Black may decline the gambit instead. The most popular and sound are 2...Bc5 and 2...d5.

It's important to realise two things: Black can't immediately exploit the weakened e1-h4 diagonal (2...Qh4+? 3. g3! and the queen has to go back) but they could were White to move their f-pawn. Therefore, White isn't really threatening fxe5 yet. That is to say, Black doesn't need to defend the e5-pawn directly, (say with 2...d6!?) because if White takes on e5, Black has the reply ...Qh4+!.

For example, 2...Bc5, the classical way to decline the gambit, and if 3. fxe5?? Qh4+! 4. g3 (4. Ke2?? Qxe4#) Qxe4+ picking up the rook on h1. 3. Nf3 is the main move: controlling h4 so that fxe5 (or Nxe5) is now a threat, 3...d6 to defend the pawn then White has a variety of plans including c3 & d4 and building a mammoth three pawn centre. Overall 2...Bc5 gives an even game and avoids the fireworks of the king's gambit accepted, but other than setting a few traps is not as critical of White's play.

2...d5, the Falkbeer countergambit, is the main way of declining the gambit in modern times. 3. exd5 exf4 4. Nf3 Nf6 is the main line: Black still takes the pawn on f4, but rather than holding on to the extra material, they want to trade it for an open position and easy development. With an open position and active pieces, Black expects that, all other things being equal, they must come out on top eventually due to White's king's side weaknesses.

2...Nc6, the queen's knight defence, is the most common way of declining the gambit in amateur games. After 3. Nf3, preventing ...Qh4, 3...d5 4. exd5 Qxd5 5. Nc3⩲ scores tempo on the queen. At higher levels the main idea is 3...f5, the Miles defence.

Other possible approaches, in roughly descending order of legitimacy, are:

• 2...Nf6, resembling a reversed Latvian gambit, was suggested by Petroff.
• 2...c5?! is the Mafia defence.
• 2...f5? is a dubious countergambit sometimes called the Panteldakis countergambit. Black volunteers to sabotage their king's side too, which White gets to exploit e.g. 3. exf5 exf4? 4. Qh5+. In the game Kennaugh vs Shirazi, the game continued 3...e4?! 4. Qh5+ Ke7 5. d3 Nf6! 6. Qg5?!, and Black went on to win a wild game.^[1]
• 2...Qf6?, the Norwalde variation, is playable but at best a mistake of missed opportunity.
• 2...f6?, bad.
• 2...g5??, called the Zilbermints double countergambit, is irredeemable.

The king's gambit is one of the oldest recorded openings. It was extremely popular during the Romantic era of chess, when attacking, tactical chess was in vogue and it was seen as unsporting to decline a gambit. Open any 19th century book of analysis and you will see it was regarded as one of the main-est of main lines.

This admirable opening, in which is comprehended every variety of the game... gives birth to the most intricate and beautiful combinations of which the chess-men are susceptible
―Howard Staunton^[2]

In 1851, the opening was played in what would be come one of the most famous chess games of all time, the Immortal Game, where Adolf Anderssen as White sacrificed twenty-one points of material and mated their opponent.

Towards the end of the century, the popularity of the gambit declined with improvements in technique for Black and as Steinitz's new "positional" chess began to displace Romantic chess. By the 1930s, Tarrasch wrote that the strength of the defences 2...d5, 2...Bc4, or 2...exf4 3. Nf3 Nf6, rendered the king's gambit:

a decisive mistake... it is almost madness to play
―Siegbert Tarrasch^[3]

In 1968, Bobby Fischer published a famous monograph advocating the continuation 2...exf4 3. Nf3 d6, the Fischer defence, as a refutation.

The gambit is uncommon in serious tournament chess, as White gives up their advantage against a well-prepared opponent. However, it is still playable as a surprise weapon in faster time controls and popular in amateur games.

1.e4 e5 2.f4

Wikipedia has related information at King's Gambit.

• Nunn's Chess Openings. 1999. John Nunn (Editor), Graham Burgess, John Emms, Joe Gallagher. ISBN 1-8574-4221-0.

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.