Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Bc5/4. c3/4...Nf6/5. d4/5...exd4/6. b4/6...Bb6

= Dubov Gambit =

6...Bb6
Black retreats his bishop to b6. White cannot recapture the d4 pawn without hanging the b4 pawn. White can continue with '''7. e5'''.

Theory table
'''1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d4 exd4 6. b4 Bb6'''