patzer2: While 21...g6? may be weak, the reply 22. d5!! is a very strong and subtle "deflection" move. Because of the threat 23. dxe6, Black is forced to either capture the pawn (22...cxd5; 22...Nxd5) or move his Rook (22...Re5; 22...Re7; 22...Re8). Unfortunately for Black, White wins in all these variations:A. [22...cxd5 23. Rc8+! (not 23. exd5?? Rxe3
; missing the sure win is 23. Nxd5?! Nxd5 24. Qxd5
) 23...Ne8 (23...Re8 24. Nxd5!
; 23...Kg7 24. Nf5+ gxf5 25. Qg5#) 24. Ng4!! (also winning is 24. Nxd5! Qb5 25. Qd4 Ra5 26. Nf6+ Kf8 27. Rdc1
) 24...dxe4 (24...Kg7 25. Qh6+ Kg8 26. Nf6+ Rxf6 27. Rxe8#) 25. Rxe8+! Rxe8 26. Nf6+ Kf8 (26...Kg7 27. Nxe8+
) 27. Qh6+! Ke7 28. Nd5+
]
B. [22...Nxd5 23. Nc4! 24. exd5
]
C. [22...Re5 23. Nc4! Qc7 24. Nxe5
]
D. [22...Re7 23. Nc4! Qc7 (23...Qd8 24. Qd4
is this game's finale) 24. Qd4 b5 25. Na3 Ne8 (25...Kg7 26. Rxc6 Qb8 27. Nxb5! Qxb5 28. Rxd6
; 25...Re5 26. Nxb5
) 26. Nxb5 c5 27. Qc3 Qb6 28. Nxa7
]
E. [22...Re8 (gives Black the most resistance) 23. Nc4! Qd8 (23...Qa6 24. Nxd6
; 23..Qc5 dxc6
; 23...Qc7 24. Qd4 b5 25. Na3 Qe7 26. dxc6 Rb8 27. c7!
) 24. dxc6 bxc6 25. Nxd6 Rd7 26. Rxc6 Qe7 27. Qd4 Red8 28. e5 Ne8 29. b3 axb3 30. axb3
]
Note: You may find a computer helpful in figuring out some of the complicated subvariations after 22...Re8 (e.g. 22...Re8 23. Nc4! Qa6 24. Nxd6 gets very complicated, with a lot of nice tactics). Because it puts up the most resistance with the best chance to pull off a swindle, 22...Re8 is the move Black should have played.