C47 Four Knights Game

ECO code C47 covers the Four Knights Game, reached after 1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6, in the branches where White plays neither the Spanish nor the Italian bishop move on move four. The main option is the Scotch Four Knights, 4.d4 exd4 5.Nxd4. White opens the centre at once, and after 5...Bb4 6.Nxc6 bxc6 7.Bd3 White aims for e5 or quick castling, while Black, with doubled c-pawns, looks for ...d5 to challenge e4. The quieter 4.g3 prepares Bg2 to press on the long diagonal and keeps the option of a later d3 or d4.