Black runs into a known opening trap and couldn't recover from that. An excellent example of clearance: 21.Nd5! sacrifices the knight to make b6 available for the bishop (Nxd5? Bb6+) and opens the diagonal for the Queen.

mephisto2    --    eddiet
   redhotpawn
2003.08.28     1-0     B49j


1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nc6
this moves brings us to the Taimanov variation. Can easily transform into a Paulsen also named Kan (with a6) or a Scheveningen (with d6).
5.Nc3 a6 6.Be2 Qc7 7.O-O Nf6 8.Be3 Bb4 9.Na4 (D)

BR :: BB :: BK :: BR
:: BP BQ BP :: BP BP BP
BP :: BN :: BP BN ::
:: :: :: ::
WN BB WN WP :: ::
:: :: WB ::
WP WP WP :: WB WP WP WP
WR :: WQ :: WR WK

this is one of the mainlines of the Taimanov (an alternative is 6.g3). The idea of Na4 is make c4 available, as well as to play later on Nb6 followed by Nxc8, giving the bishop pair to white in a more or less equal position. This can happen with both 9. ... 0-0 and 9. ... Be7.
9...Nxe4?
But pawn e4 is not covered, and looks so attractive.....
10.Nxc6 Qxc6 11.Nb6 Rb8 12.Qd4!
attacks the bishop, the knight (still covered by Qc7) and g7
12...Bf8 13.Bf3
nasty pin of the knight
13...f5
the alternative was 13. ... d5 14.Bf4 Nd6 15.c4 threatening c5
14.Rad1 Rg8 15.Bxe4 fxe4 16.f3
opening more lines
16...exf3 17.Rxf3 d6 18.Qf4
the attack is unstoppable now
18...Qc7 19.Rdf1 Qe7
the only move avoiding checkmate
( 19...e5? 20.Qxf8+! Rxf8 21.Rxf8+ Ke7 22.Bg5+ Ke6 23.Re8+ Qe7 24.Rxe7# )
20.Qa4+ Kd8
Bd7 gave more resistance:
( 20...Bd7 21.Nxd7 b5 22.Qe4 Kxd7 23.Qxh7 wins the rook on g8 )
21.Nd5! (D)

BR BB BK BB BR ::
:: BP :: BQ BP BP
BP :: BP BP :: ::
:: :: WN :: ::
WQ :: :: :: ::
:: :: WB WR ::
WP WP WP :: :: WP WP
:: :: :: WR WK

a clearance sacrifice. The knight leaves b6 at any cost.
21...Bd7
( 21...exd5? 22.Bb6+ Qc7 23.Rxf8+ Rxf8 24.Rxf8+ Ke7 25.Qe8# )
22.Qa5+
black resigns. He loses the queen ( 22. ... b6? Bxb6+).
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