Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Bc5/4. Bxf7

4. Bxf2+? is the unhinged Jerome gambit. Though a Bxf2+ sacrifice works in many lines in the Italian, this is far too early and it is objectively woeful for White. However, it is sharp enough that White has some success at the club level.

The idea is 4...Kxf7 5. Nxe5+ Nxe5 6. Qh5+, and White hopes that between Black's exposed king and the skewering of Black's pieces on the fifth rank they will swindle compensation. e.g. 6. Qh5+ g6 7. Qxe5 d6?? (better is Qe7∓) 8. Qxh8±.

After 4...Kxf7 5. Nxe5+ Nxe5 6. Qh5+ there are several winning approaches for Black. The engine line involves marching their king out to into the middle of the board to guard the bishop: 6...Ke6 7. Qf5+ Kd6 8. f4 Kc6 9. Qxe5 Nf6-+ etc, and despite the weakness of their enemy's king, White's queen alone can't sustain an attack.

The simplest approach is to just return the bishop, 6...Ng6 7. Qxc6∓. White has only captured two pawns in exchange for their knight, and the only piece they have developed is their queen. Black can come out swinging.

So named for Alonzo Wheeler Jerome, who wheeled it out against William Shinkman in 1874.^[1] Joseph Blackburne referred to it as the "Kentucky opening".^[2]

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

1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. Bxf7

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Wikipedia has related information at Jerome Gambit.