Wikipedia:List of hoaxes on Wikipedia/Ruy Lopez, Marshall Attack, Rombaua Trap

The Rombaua trap is a chess trap in the Marshall Attack for Black against the Ruy Lopez opening for White. Instead of the standard 13...Qh4, Black plays a surprise greek gift sacrifice with 13...Bxh2+.

The trap
'''1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. 0-0 Be7 6. Re1 b5 7. Bb3 0-0 8. c3 d5 9. exd5 Nxd5 10. Nxe5 Nxe5 11. Rxe5 c6 12. d4 Bd6 13. Re1'''
 * The opening moves of the Ruy Lopez, Marshall Attack. Now 13...Qh4 is the main line continuation with a dangerous attack on White's kingside.

13... Bxh2+
 * The Rombaua trap is a more aggressive line beginning with Black's sacrifice of the dark-square bishop. White is delighted to accept the free bishop.

'''14. Kxh2 Qh4+ 15. Kg1 Bg4 16. Qd3 Rae8''' (see diagram)
 * White's Qd3 is a routine move in the Marshall Attack.

17. Be3?
 * Falling into the trap. The natural-looking move 17.Be3 blocks the threat from Black's rook while developing the white bishop to its regular post. The games Mikhail Tal vs Efim Geller, URS 1975; and Judit Polgar vs John Nunn, Muenchen 1991 are among the fine examples of the casual Qd3 and Be3 in the Marshall. A computer program will however give a very unnatural 17th move for White, the antidote for the trap. But more often than not White continues thematically in the Marshall Attack, namely 17.Be3 or 17.Bd2, as the need to develop the bishop seems logical and tempting.

17... Nf4
 * A tactical move by Black, exploiting the bishop's inability to defend the critical f4-square. To an unprepared opponent, this move is difficult to anticipate; and to a better human opponent, it looks like an empty move by Black since the knight has no promising square to go to after Nf4. 17...Nf4 is also effective against 17.Bd2, which puts White into a deeper trouble because of the threats Rxe1+ and Ne2+.

18. Qf1 Nh3+
 * To a White player still believing in his material advantage and that 13...Bxh2 was just an erroneous sacrifice, the sacrifice of the knight may appear that Black is desperate and nearly ready to resign. But in reality White's position is already doomed.

'''19. gxh3 Bxh3 20. Qe2 Re4'''
 * In response to 20...Re4, some computers recommend 21.Bd1 giving up White's queen. This leaves White a small material advantage, but his king is still in the open which can easily be exploited.

21. f3 Qg3+
 * If instead 21.f4, 21...Qg3+ followed by ...Rxe3 wins since White's queen is overworked defending both the e3- and g2-squares.

22. Kh1 Rh4
 * White resigns.