According to Crafty, after 24...bxc4 Black has a -1.90 advantage

I was reading about this game in Seirawan's "Winning Chess Strategies" and I thought 24...bxc4 was a better move

I don't know why Seirawan did not include analysis of that line in the book. Space and complexity of tactics may not have been a fit with the editor.

After <24..dxc4 25.Bc2> Seirawan would have nice attacking prospects, with Bxf6, Bg6 and Re1 all in the air. If Black cannot find a reasonable defense to <26.Bxf6 gxf6 27.Bg6 Nxg6 28.hxg6> then he is lost.

Black's K safety is the key to the position. Korchnoi's 24..Bxc4 is trying to exchange one of his offside pieces for Seirawan's active bishop on b3.

Should white exchange rooks or play Re1? When does he have time for the h-file rook lift? When does Bxf6 work?

For Black, if he gets in Qxa2, he not only put pressure on f2 but after c3 he can cover the light squares on his porous K-side. Running interference with ..Rd3 also looks interesting.

Victor took me aside to speak with me in private. He explained he would soon be playing his Candidates' Match against an arch-rival, Tigran Petrosian. "Would I like to be his second?" I was dumbfounded and didn't know how to answer. I'm quitesure nothing came out of my mouth as I stood there in shock. I can honestly say that my tumultuous thoughts centered around one concept only: how much would it cost me and could I afford it?

Victor completely misunderstood my silence. "Oh!" Victor said, "Sorry. The conditions are: I pay your travel, hotel and meal expenses. While you are working with me, I pay you 500 Swiss francs a week..."

Now I was convinced I was dreaming. Did I understand that right? Victor was offering to pay me? To train him? What on earth could I teach Victor Korchnoi? I gratefully accepted and stuck out my hand in agreement. Shake.

Literature source: Chess Duels: My Games with the World Champions by Yasser Seirawan >>> http://www.amazon.com/Chess-Duels-G...

<"Luck, luck, luck," Seirawan now says of that match. "You can be lucky. I'm unknown to the guy. So he decides to play a second-rate defense to improve his offensive chances. Heh! This defense is the one and only thing I know like the back of my hand. He falls right into it. Like into all my preparation, all my traps! I knew it from a lot of blitz games. I spring an opening novelty; I sacrifice two pawns; I whip out a kingside attack and make a space." Voilà!

Korchnoi resigned on the 39th move. A bit stunned, he offered his hand. "Congratulations," he said. "Good game." No doubt the last thing Korchnoi wanted to do was sit and gab with this child from Seattle. Seirawan suspected that Korchnoi really wanted to go back to his room and chew up his sofa. But Seirawan offered him some popcorn anyway. "Gee, Viktor, you want to go over the game?" How could Korchnoi refuse? They repaired to an analysis room and went over it, move by move.

Korchnoi grew curious. "What would you have done if I'd taken your knight here?" he asked.

"You know, Viktor, I expected that," said Seirawan. They played variations, and each time Seirawan exposed the weakness in Korchnoi's idea. Seirawan was lucky. However Korchnoi figured it, Seirawan knew the moves. The grandmaster had fallen into Seirawan's pet line.>

"You know, Viktor, I expected that," said Seirawan.>

Err...at what point in the game was taking White's knight an option?!?>

After 24....dxc4, which is what I assume zooter had in mind, 25.Bxf6 is winning, but SF's favorite is 25.Bc2, and if 25....c3 26.Bb3! Ke8 27.Bxc3!. If 27.....Qxc3 28.Be6 is winning. Or 25....Bb4 26.Qh8+ Ng8 (26....Kf7? 27.Bg6+! Nxg6 28.hxg6+ Kxg6 29.Rxh6+!) 27.Nd4 Bc8 28.Rh4 Bd7 29.Bh7 Qd5 30.Re4 threatening Ne6+ -- there doesn't seem to be a defense (SF).

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Amazing how Korchnoi arrived at <12... Bc5> almost purely by process of elimination. "I calculated all the other moves in the position, they all lose, Bc5 it is."