Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. c3/3...Nf6/4. d4/4...Nxe4/5. d5/5...Bc5

Black gambits their knight on c6 with 5...Bc5, the Vuković gambit or Fraser defence. Black's c5 bishop and e4 knight both target White's f2 pawn.

The Vuković gambit is so bloodthirsty that if Frankenstein and Dracula ever take a break from the Vienna game, expect to see them here.^[1] Accepting the gambit, 6. dxc6, is the engine recommendation but perilous. With best play from both sides, Black maintains a small edge by engine but huge success in practice.

White must accept the offered knight with 6. dxc6, leading to a chaotic and cut-throat middle game where both Black and White must navigate a series of only moves to keep the game competitive, or make a huge concession to Black with 6. Be3?. Trying to defend f2 with 6. Qe2?? avoids 6...Bxf2+ but fails to 6...Nxf2.

After 6. dxc6, Black has a choice of ...Nxf2 or ...Bxf2+. 6...Nxf2? loses to 7. Qd5, where, if Black takes the rook, they will lose their bishop and their knight gets stuck. Therefore Black must play 6...Bxf2+□.

After 6...Bxf2+ 7. Ke2, Black must retreat the bishop 7...Bb6. This is because White can too easily dislodge the knight defending f2.

• 7...bxc6? is a mistake because Black can't keep the bishop and knight defended. 8. Qa4 f5 9. Nbd2±.
• 7...O-O? is a mistake because Black can dislodge the knight with 8. Nbd2. 8...Nxd2 9. Kxf2±, or 8...f5 9. Nxe4 fxe4 10. Qd5+ Kh8 11. Qxe4±.

After 7...Bb6, Black threatens ...Nf2 but White should not try to prevent it:

• 8. Be3?!, White's only way to to control f2, is closing stable door after the horse has bolted. 8...bxc6∓ and Black has three pawns for the knight and a much better position.
• 8. Qd5!□ is White's best move: defending c6, attacking e5 and the knight on e4, and avoiding Nf2 from gaining tempo on the queen.

After 8...Nf2, attacking the rook, White has the illusion of choice: save the rook with 9. Rg1, counterattack with 9. cxb7, supported by the queen on d5, or take the e5 pawn with check 9. Qxe5+?.

The e5 pawn is poisonous of course. If 9. Qxe5+? Kf8, now 10. cxb7? doesn't work (10...Bxb7) and after 10. Rg1 Ng4 (wins tempo on the queen) 11. Qf4 dxc6 the knight is defended by Black's light square bishop. White might have been hoping to support 10. Be3 to eliminate Black's powerful bishop, but Black can simply play 10...Nxh1.

So White must choose from 9. Rg1 or 9. cxb7.

Should White save the rook 9. Rg1, Black must allow cxb7. Otherwise,

• 9...bxc6? 10. Qxe5+□ (this time e5 is not poisonous) Kf8 11. Nd4□ (interrupts bishop's vision of knight) Ng4 12. Qf4 and Black's attack is diffused. Needless to say, anything other than 10. Qxe5+ or 11. Nd4 is losing for White.
• So Black must play 9...O-O□ instead, knowing to sacrifice their bishop after 10. cxb7 Bxb7 11. Qxb7 with the recognition that their queenside is stable. Black should continue 11...Qf6□ to allow 12...Rab8 Qd5 to be met by c6.

Should White counterattack, 9. cxb7, then 9...Bxb7 10. Qxb7 Nxh1⩱. Black has the rook and two pawns but is down two minors, and the position is still chaotic. White can follow with 11. a4, planning a5, b4 to kick the bishop, and trap Black's knight.

The advantage for Black is that these tactical middle games, with White's king exposed on e2, are far from the calm, central development that White hoped for when they played 3. c3. The advantage for White is that Black has gambitted a minor piece and it is up to them to prove they have compensation. Of course, navigating a string of only-moves is only precarious if the other side can pick up when you mis-step.

White may try 6. Be3?, trading bishops and 6...Bxe3 7. fxe3 avoids the complications following 6...dxc6. This gives Black's knight the chance to escape, and though White can win a pawn with 7...Ne7 8. Nxe5, they have difficulty developing and keeping their backwards e3 pawn defended. For example, 8...O-O 9. Bc4 (defending d5 and trying to castle) Nf5 (attacking e3) 10. Qf3 Ned6 (attacking bishop on c4) 11. Bb3 Re8 (attacks knight on e5 and pins knight to pawn) and White is cooked.

6. Be3? avoids the complications following 6...dxc6, however it is unsound and the resulting positions are favourable for Black. Despite being an inferior continuation by engine, this line brings White more practical success than the 6...dxc6 line.^[2] This is a testament to how difficult it is for White to navigate the 6. dxc6 line. Another factor is that after 6. Be3? White sets a trap for Black: 6...Bxe3 7. fxe3 Ne7 8. Nxe5, the most common move 8...d6?? gives up Black's advantage. 9. Qa4+!□ c6 10. dxc6 bxc6 11. Nxc6 (attacking the queen) ± wins White a pawn, and 11...Nxc6?? is a blunder because after 12. Qxc6+ Bd7 Black's knight is hanging.

6. Qe2?? defends the pawn and attacks Black's knight. This nullifies the threat of 6...Bxf2+??: 7. Kd1 and both of Black's knights are hanging. Black must give up the knight on c6 and play 7...f5 to defend the knight on e4, which protects the bishop, and their attack fizzles out.

However, 6. Qe2?? doesn't prevent 6...Nxf2!. The best White can do is save their rook and let Black's c6 knight escape (7. Rg1 Ne7∓), and Black is up two pawns.

5...Bc5 was played by Ernst Falkbeer (1819―1885) in 1855, with the continuation 6. dxc6 Nxf2?!.^[3]

Mikhail Chigorin (1850―1908) first played 6...Bxf2+ in 1879, in St Petersburg against Eugen von Schmidt.^[4] It was an improvement over the 5...Nb8 line he had played against von Schmidt in an earlier round.^[5]

After 7. Ke2, 7...bxc6? was thought to be Black's best continuation, and for a century the gambit was thought to be refuted by 8. Qa4.^[6]:49-53 7...Bb6 was tried once by de Rooi in 1964 which continued 8. Be3?! bxc6 9. Bxb3 axb3.^[7]

It was not until the 2000s that 7...Bb6 was revived and 8. Qd5! played. An early outing of the modern form of the gambit was in the 2008 US Women's Cup, Epstein v Batchimeg.^[8]

For explanation of theory tables, see theory table and for notation, see algebraic notation.

1. e4 e5 2. Nf3 Nc6 3. c3 Nf6 4. d4 Nxe4 5. d5 Bc5

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Wikipedia has related information at Ponziani Opening

• Taylor, Dave; Hayward, Keith (2010). Play the Ponziani. London: Everyman Chess. ISBN 1 8574 4620 8.