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 considered one of the most dangerous, crazy lines in all of chess due to its wide range of tactical motifs.

Accepting the gambit, 6. dxc6, is the engine recommendation but perilous. It leads 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. 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] 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 and brave the cliff edge, 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, 6...Nxf2? loses to 7. Qd5, where, if Black takes the rook, they will lose their bishop and their knight gets stuck. Black must play 6...Bxf2+□.

After 7. Ke2, 7...bxc6? is a mistake because Black can't keep the bishop and knight defended (8. Qa4 f5 9. Nbd2). Black must retreat the bishop, 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. Instead, White's best move is 8. Qd5!□, 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.

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 give up their rook and counterattack instead 9. cxb7, 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 cliff edge of only-moves is only precarious if the other side can pick up when you mis-step.

White may try 6. Be3?? trading bishops; however, this allows Black to damage White's central pawn structure and demolish White's vulnerable pawn center with careful play. 6...Bxe3 7. fxe3 avoids the immediate complications following 6...dxc6, but the resulting positions are winning for Black due to a substantial development advantage and the threat of tactics on e4. This gives Black's knight the chance to escape, and though White can win a pawn with 7...Ne7 8. Nxe5, White has difficulty developing, keeping their backwards e3 pawn defended, and holding their flimsy center together. In fact, after 8...O-O, even this line often devolves into insane tactical skirmishes with Black hammering at White's center.

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.

It's a testament to how difficult the 6. dxc6 line is to play that 6. Be3?? brings White slightly more practical success, despite being a losing blunder.^[2] However, 6. Be3?? only delays Black's tactical onslaught by a few moves, as Black has time to consolidate before attacking White's position.

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...Bd6 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.