C45 Scotch Game

ECO code C45 covers the Scotch Game proper: 1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4, where White opens the centre at once and recaptures with the knight. Black has two main replies. 4...Bc5 is the Classical Variation, in which the bishop hits the d4 knight. White can answer with 5.Nxc6, when 5...Qf6 threatens mate on f2; with 5.Nb3, which attacks the bishop; or with 5.Be3, defending the knight, met by 5...Qf6 and 6.c3 Nge7. The other main reply, 4...Nf6, leads to the Mieses Variation: 5.Nxc6 bxc6 6.e5 Qe7 7.Qe2 Nd5 8.c4. White gains space and drives the knight, and Black's 8...Ba6 pins the c4 pawn against the queen on e2.