The solid 4th - Bc5
Early queen excursions are back in fashion
1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Bc5
The natural development move 4...Bc5 is the second and older main variation against the Scotch Game. Here Black develops their bishop with tempo against Nd4, which is attacked a second time. White must now decide whether to retreat the knight with 5.Nb3, exchange with 5.Nxc6 or defend once more with 5.Be3.
The retreat 5.Nb3 is a simple continuation that avoids complications, but is not often played today. Black saves their bishop from being exchanged with 5...Bb6 and should have no major worries.
The knight exchange 5.Nxc6 is answered with the intermediate move 5...Qf6, which threatens mate on f2. White must now fend off mate with an uncomfortable queenside move, either 6.Qf3, which after 6...Qxf3 7.gxf3 worsens the white pawn structure, or 6.Qd2, which blocks the Bc1. After 6.Qd2 Black usually accepts a double pawn with 6...dxc6 in favour of rapid development.
The most important move for White after 4...Bc5 is the defence of the knight with 5.Be3, which looks logical, because why should the white central knight voluntarily vacate its post. However, Black can now attack this knight a third time with the amateurish-looking queenside move 5...Qf6 and force a concession.
Either White now tries the sharp, but very dubious 6.Nb5, or they reliably cover the centre knight with 6.c3, but this deprives the queen's knight of its natural development square. The sharp 6.Nb5 is followed by 6...Bxe3 7.fxe3 (7.Sxc7+ fails with 7...Kd8, which threatens mate on f2 and ...Kxc7) with a gruesome double pawn on the e-file:
Black can choose between the retreat 7...Qd8 or 7...Qh4+ 8.g3 Qd8 or the sharp counter-attack 7...Qh4+ 8.g3 Qxe4.
The reliable 6.c3 Nge7 is the main variation, and in this position the move 7.Bc4 revitalised the whole line in 1991. After 7...Ne5 8.Be2 Qg6 9.0-0 d6
White can protect the e4-pawn with 10.f3 or choose a sharper line with 10.Kh1 or 10.f4 and offer a pawn sacrifice. As in many other variations of the open games, the early double move of the d-pawn guarantees free play with simple piece development. Above all, Black must understand why they are allowed to bring out the queen so early in this variation.