Budapest Gambit

Almost a respectable opening.

— Boris Avrukh^[1]

2...e5 is the energetic Budapest defence, aka the Budapest gambit. Black challenges White's centre straight away. Black sacrifices a pawn, but can usually recover it, in return for active play. It's one of those slightly inaccurate sort of lines that is usually described as a "good blitz/surprise weapon".

3. dxe5, accepting the gambit, is the main line. White takes the pawn and compels Black's knight to move again, either to g4 or e4. White is up a pawn but it may be a mistake to hold onto it too tightly. Returning it allows White to avoid tactical complications (in the main line continuation, it is returned after 3...Ng4 4. Bf4 Nc6 5. Nf3 Bb4+ 6. Nbd2 Qe7, and White cannot add a further defender).

Declining the gambit is atypical. Surely Black shouldn't be allowed a free potshot at White's centre?

• 3. e3?! prepares to recapture the pawn, but allows Black to equalise. A continuation is 3...exd4 4. exd4 Bb4+ 5. Nc3 O-O 6. Bd3 d5=^[2].
• 3. Nf3?! to defend the pawn allows 3...e5 to drive the knight away.
• 3. d5?! to avoid the capture is a positional mistake, and releases the c5 square for Black's bishop.

The Budapest is first known from a 1896 game between amateur Mór Adler and Géza Maróczy (1870―1951) in Budapest.^[3] It was revisited in 1916, again in Budapest, by Gyula Breyer (1893―1921) as Black against Johannes Esser (1877―1946)^[4] and came to prominence when Milan Vidmar (1885―1962) scored an upset with it against Akiba Rubinstein (1880―1961).^[5]

1. d4 Nf6 2. c4 e5

Wikipedia has related information at Budapest Gambit.