The postponed Poison Pawn variation of the Najdorf Sicilian.
9.Qd2!? Accepting the challenge is the most principled decision. [White does not have to sacrifice the pawn and can play 9.a3 Be7 (9...Qxb2? 10.Na4 wins.) 10.Bf2 with good play.]
9...Qxb2 10.Rb1 Qa3 11.e5 dxe5 12.fxe5 g5 A sharp variation, leading to playable game for black. [The second popular line is rather unbelievable: 12...Nfd7 13.Ne4 Qxa2 14.Rd1!? (14.Rb3 Qa1+ 15.Kf2 Qa4 is good for black.) 14...Qd5 15.Qe3 Qxe5 16.Be2 and despite being three pawns down, white pieces radiate a lot of energy.]
13.exf6 gxh4 Up to here, the line is rather forced.
14.Be2 Nd7 15.0-0 Qa5 16.Kh1 Qg5 17.Qe1 According to GM Lubomir Ftacnik, this move was tested three years ago 2,500 times in computer games, while humans ventured there only a few times. [The main choice in this position was 17.Rf4 e5 18.Nd5 exd4 19.Qxd4 with a good compensation for the piece.]
17...Nxf6!? An improvement. [After the previously played 17...Bd6 18.Ne4 Qe5 19.Nxd6+ Qxd6 20.Qxh4 white has a big advantage.; The computers suggest 17...h3 18.gxh3 Qe5 19.Nf3 Qe3= ]
18.Nf3 Qc5 [Black wants to keep his queen active, but 18...Qg7 19.Nxh4 Be7 20.Bf3 0-0 is roughly equal.]
19.Na4 Qc7 20.Nb6 Rb8 21.Qxh4 Be7 22.Qd4 Trying to secure the square e5 for his knight.
22...Rg8 23.Ne5 Rg5 24.Ng4 Nxg4 25.Bxg4 f5? A reckless move and white finds the refutation. [Black should have tried 25...Bc5 26.Qh8+ Bf8 (26...Ke7 27.Rxf7+ Kxf7 28.Qh7+ Rg7 29.Rf1++- ) 27.Bf3 Qe5 ]
26.Bxf5! Robson might have overlooked this sacrifice. White gets a strong pressure on th e-file.
26...exf5 [Or 26...Rxf5 27.Rxf5 exf5 28.Re1+- ]
27.Rbe1 Kf8 28.Qh8+ [This should win, but 28.Nd5 Qd6 29.Rxe7 was even better.]
28...Rg8 29.Qxh6+ Rg7 30.Nxc8 Qxc2 Suddenly, black is threatening a mate and Yu gets nervous. [But not 30...Rxc8 31.Rxf5+ Kg8 32.Qe6+ Kh8 33.Rh5+ Rh7 34.Rxh7+ Kxh7 35.Qf7+ Kh8 36.Rxe7+- ]
31.Qh8+ Rg8 32.Qh3 [White misses a winning tic-tac-toe combination: 32.Rxf5+! Qxf5 33.Qxg8+! Kxg8 34.Nxe7+ Kf7 35.Nxf5+- ]
32...Rxc8 33.Rxf5+ Ke8 34.Qh5+? The last moment when white misses the win, but the combination is not easy to calculate for human players. The computers provide the answers: [34.Rxe7+! Kxe7 35.Qh7+ Kd6 36.Rf6+ Ke5 (36...Kd5 37.Qd7+ Kc5 38.Qe7+ Kb5 39.Qxb7+ Kc4 40.Rf4+ Kd3 41.Qd5+ Ke2 (41...Kc3 42.Qd4# ) 42.Qe5+ Kd1 43.Rf1+ Kd2 44.Rf2+ Kc1 45.Qa1+ Qb1 46.Rf1++- ) 37.Qe7+ Kd4 38.Rf4+ Kd3 (38...Kd5 39.Qd7+ Kc5 40.Qd4+ Kb5 41.Qb4+ Kc6 42.Rf6+ Kd5 43.Rd6+ Ke5 44.Qd4+ Kf5 45.Rf6+ Kg5 46.Qf4+ Kh5 47.Rh6# ) ; White also has 34.Rf2 , trying to deflect the queen, but it is not as strong. ]
34...Kd8 White lost the thread and the black king is escaping.
35.Rd5+? The wrong check. White had to play [35.g3 ; or 35.Qf3 ]
35...Kc7 36.Qe5+ Kb6 37.Re2 Qb1+ 38.Re1 Qxa2! 39.Qe4 Qc2! Robson played two precise queen moves and the flashy combination is easily twarthed.
40.Rb1+ Ka7 41.Rxb7+ Ka8! The refutation. White is weak on the first rank and his pieces are hanging. [But not 41...Kxb7? 42.Rb5+ Kc7 43.Qxe7+ Kc6 44.Qb7+ Kd6 45.Rd5+ Ke6 46.Qd7+ Kf6 47.Qd6+ white wins.]
42.Qf3 Qxg2+! The final mating combination.
43.Qxg2 Rc1+ [43...Rc1+ 44.Qg1 Rcxg1# ] 0-1