I also wonder where can that trap be. Schussler analyzed this game and came out with a somewhat tricky response to the "natural" 21.Nb5 (Which for sure Karpov´s team had looked at):

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21...Qd7 22.Qc4 c6 (which he conceeds an exclamation mark)

But I totally fail to see the trap even in this line, nor in the 21...Bxb2: there are absolutely no tricky-only-moves anywhere for white as far as I can see, and even in the ...c6 variation pointed out white doesn´t have much problems defending (well, it´s true that white will have a hard time trying to win, but if the "trap" was just a drawing technique from Karpov´s team, why then they put "a lot of hope" (sic) in it?

With the inmediate 21...Bxb2 (answered by 22.Ra2, of course) the ending that can arise is a NN + 1 extra pawn vs BB, with pawns on one side of the board, something like this:

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Which is perfectly holdable from both sides.

And furthermore, I have failed to track any posterior game in this line since the Kasparov - Karpov one, so it seems like we aren´t the ones who fail to see any worthy advantage for black in here...

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And by the way, speaking about the game neither do I know why Kasparov plays, in this position:

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38.Kh2 when he can advance the pawn without problems (for him) and causing further troubles (for Karpov): there is always Nf4, forking and defending g2 also, if ...Bxh2

One idea what you do when you cannot quite get to grips why a move you think was OK and yet was not played, is to look at what was actually played.

If GilesFarnaby had played through the game he would not have been so baffled with Kasparov playing here:

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38.Kh2.

The answer is simple. Kasparov's next move was 39.f4 if he plays f4 before Kh2 then Black can play 39...Bxh3 and White has no Nf4 defence.

Also you have to mention prophylactic idea behind getting away from diagonal or back rank checks.

Whether pushing the b-pawn was better than the f4 plan is not an issue. Kasparov wanted to play f4 and Kh2 prepared this.

The Mystery of the b2 Pawn.

Again see how the game was actually played.

Karpov judged his weak c7 pawn needed tending too before taking on b2.

Kapsarov too must have liked what he saw coming because he was prepared to let the b2 pawn go.

Here:

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Kasparov could have saved the pawn with 21.Qd2 then Black can play 21...c6. He played 21.Qc4.

So both these two great players have judged the weak c7 pawn is a critical weakness. One is willing to sac a pawn to keep it weak - the other is willing not to take the pawn to repair it. Hence 21...Qc8 instead of 21...Bxb2.

Up to here Karpov had used 16 minutes so we are still in his home prep. He then spent 1 hour and 3 minutes on 21...Qc8 (the longest think in the whole match - Kasparov took 9 minute to come up with 21.Qc4!).

So he knew he was making a critical decision trading the c7 weakness for a weak d6. (position 4 moves later.)

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This was what he judged over the board as his best option. Karpov's over the board decisions won him a lot more games than he lost. Here you can see one idea is to hold the weak d6 pawn actively with Re6 and Rg6. (that happened in the game...always look at what was played, then you can often figure why other moves were not played.)

He played what he wanted to play. He just did not fancy defending that c7 weakness judging Kasparov's game would be easier to play. Karpov made a living out of winning such positions, he knew what he would be facing and simply chose not to go that way.

I never overlooked it. That is what I am saying.

Karpov opted to rid himself of the c7 weakness rather than take the b2 pawn.

Kasparov offered the b2 pawn as positional bait. Karpov, after a long reflection, rejected it.

If Karpov saw a line where can take the b2 pawn and safely swap that c7 pawn for the White d5 pawn I'm pretty he would have done for it.

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Some are looking for a trap. If they are looking for it with a computer they will never see it because a computer does not show traps (a trap no matter how clever) relies on a poor move. Computer don't expect them so you only get to see what it thinks is fit for you to see. It's calculation snobbery,

Kasparov's b-pawn is threatening to promote to a queen and Karpov has no good way to stop it. The king is cut off and the rook is out of position.

This is no way a draw, but an easy win for White.

The main threat is that White will advance his b-pawn and obtain a new queen. How can Black stop this?

Not with his king, which is confined by the White rook. So the only hope is the Black rook.

But how can the Black rook stop the b-pawn? Only by getting to either the 8th rank or the b-file.

The only hope is 57...Rh6+, but of course White can then play Kg2 and no way can the Black rook get to b1 (or b2, b3 etc.) So after 58.Kg2 Rh8 is forced.

But now, thanks to White's d-pawn, the White rook can push back the Black king with 59.Rc7+

Black now has 2 legal moves, 59...Ke8??? loses the rook to 60.Rc8+

This might be the most important rule in chess. Not only can you promote a pawn to a queen on the 8th rank, you can promote it to bishop, knight or rook as well.

You cannot possibly understand any endgame with pawns unless you keep this rule at the front of your mind.

https://www.theguardian.com/travel/...

Shame you didn't stop for diner.