Chess Opening Theory/1. e4/1...c6/2. d4/2...d5/3. Nc3/3...dxe4/4. Bc4

= Von Hennig Gambit =

4. Bc4
White is playing in a way reminiscent of the Blackmar-Diemer gambit, and indeed the popular lines fall into that trend. The Stockfish continuation is 4... b5, but more common are 4... Nf6 and 4... Bf5, the latter of which transposing to the main line of the former after 5. f3 exf3 6. Nxf3 Nf6. The main line after 4... Nf6 is 5. f3 exf3 Nxf3 (5... Bf5 is another line, best responded to with 6. fxe4 Nxe4 7. Qf3). In this position the main moves are 6... Bf5, 6... Bg4, and 6... e6. 6... Bg4 falls into a trap after 7. Bxf7+ Kxf7 8. Ne5+ winning a piece or the slightly worse 7. Ne5, where Bxd1 hangs Bxf7# and all other moves besides Be6 and Qc8 nearly instantly lose, while those 2 moves still leave white with a nice advantage. 6... e6 is played the most like a Blackmar-Diemer with ideas of O-O, Qe1-h4, and Bd3. 6... Bf5 is the main line, which is followed up with 7. O-O e6 8. Ng5 Bg6 (preventing Rxf5 where recaptures leads to a fork), where white's options are the calm 9. Ne2 and 9. Bf4 or the wild 9. Bxe6 fxe6 10. Nxe6, which will force black to either give up their queen or weather an incredibly dangerous attack.