411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Bc5/3. Nxe5/3...Nc6
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Chiodini gambit C40 Busch-Gass gambit
3... Nc6
Black offers to trade knights.
If White accepts, 4. Nxc6, Black will take back with the d-pawn in order to open up lines for their bishop and queen. Black has ultimately sacrificed their e-pawn for easier development. Black must then play aggressively in order to justify the sacrifice. This is a transposition into the line better known as the Stafford gambit.
The line keeps its own character if White declines the trade with 4. Nf3, from where it can support a d4 to take over space in the centre.
Theory table
Chiodini gambit accepted 4. Nxc6 dxc6 Stafford transposition 4. ... ... 5. d3 Nf6
References