King's Gambit Declined - classical - Heath variation
1. e4 e5 2. f4 Bc5 3. Nf3 d6 4. b4
White advances the king's pawn to e4. Black moves the king's pawn to e5. White pushes the f-pawn to f4.
Black develops the dark-squared bishop to c5. White develops the knight to f3. Black moves the queen's pawn to d6.
White pushes the b-pawn to b4.