The Moller Attack
Main line (Greco Attack), position after 7...Nxe4
In the main line (Greco Variation) White plays 4.c3 in preparation for the central advance d2--d4. Black can try to hold a strong point in the center at e5 with 4...Qe7 or he can counterattack with 4...Nf6. The center-holding line can continue 4...Qe7 5.d4 Bb6 6.0-0 d6 7.a4 a6 8.h3 Nf6 9.Re1 0-0.
The more aggressive 4...Nf6 was first analyzed by Greco in the 17th century. In the Greco Attack White uses a major piece sacrifice to create a trap. Play continues:
4. c3 Nf6 5. d4 exd4 6. cxd4
White can also try 6.e5, a line favoured by Evgeny Sveshnikov, when play usually continues 6...d5 7.Bb5 Ne4 8.cxd4 Bb6, with approximate equality. Instead, White has a gambit alternative in 6.0-0, which Graham Burgess revived in the book 101 Chess Opening Surprises; the critical line runs 6...Nxe4 7.cxd4 d5 8.dxc5 dxc4 9.Qe2. The other alternative 6.b4 is refuted by the strong piece sacrifice 6...Bb6 7.e5 d5 8.exf6 dxc4 9.b5 0-0! according to Jeremy Silman.
6... Bb4+ 7. Nc3 Nxe4 (see diagram)
Greco encouraged an attack on White's a1-rook with 8.0-0, allowing 8...Nxc3!? (9.bxc3 Bxc3? 10.Qb3. Now if Black takes the rook with 10...Bxa1, White wins the black queen with 11.Bxf7+ Kf8 12.Bg5 Ne7 13.Re1. This trap is now well-known, and Black can avoid it by playing 10...d5, or earlier, 8...Bxc3.) After 8...Nxc3 9.bxc3, best for Black is 9...d5! 10.cxb4 dxc4 11.Re1+ Ne7 12.Qa4+! Bd7 13.b5 0-0 14.Qxc4 Ng6!
In 1898 the Møller Attack revived this line; Danish player Jørgen Møller published analysis of the line in Tidsskrift for Skak (1898). In the Møller Attack White sacrifices a pawn for development and the initiative:
8. 0-0 Bxc3! 9. d5 (9.bxc3 and 9.Qc2 are both fine alternatives) Bf6
9...Ne5 is also interesting; a possible continuation is 10.bxc3 Nxc4 11.Qd4 f5 12.Qxc4 d6.
10. Re1 Ne7 11. Rxe4 d6 12. Bg5 Bxg5 13. Nxg5 h6!?
13...0-0 14.Nxh7! is considered to lead to a draw with best play, although Black has many opportunities to go wrong.
After 14.Qe2 hxg5 15.Re1 Be6! 16.dxe6 (White also can try 16.Qd2 c6! 17.dxe6 f6 18.Bd3 d5 19.Rg4 Qc7 20.h3 0-0-0 21.b4, attacking) 16...f6 17.Re3 c6 18.Rh3 Rxh3 19.gxh3 g6 it is doubtful that White has compensation for the sacrificed pawn, according to Grandmaster Larry Kaufman; 14.Qh5 0-0 15.Rae1 Ng6! also favors Black.
14... Bd7 15. Qe2 Bxb5 16. Qxb5+ Qd7 17. Qxb7
17.Qe2 Kf8 wins a second pawn.
and Black is at least equal.
If White does not want to gambit material, instead of 7.Nc3 he can play 7. Bd2, which can continue 7... Bxd2+ (Kaufman recommends 7...Nxe4!? 8.Bxb4 Nxb4 9.Bxf7+ Kxf7 10.Qb3+ d5!? [10...Kf8 11.Qxb4+ Qe7 12.Qxe7+ Kxe7 is safer, reaching an equal endgame] 11.Ne5+ Ke6! 12.Qxb4 c5!?) 8. Nbxd2 d5 9. exd5 Nxd5 10. Qb3 Nce7 (10...Na5 is an alternative, inviting a repetition of moves after 11.Qa4+ Nc6 [threatening 12...Nb6] 12.Qb3 Na5) 11. 0-0 0-0 12. Rfe1 c6. In this position White has more freedom, but his isolated d-pawn can be a weakness. Note: 7.Nd2 is also a viable choice of move for white, although this still only offers approximate equality. It has not been a popular choice among human players, but it seems to be recommended by computer engines.