After Gelfand centralizes his knight with 35 ... d4?, Gazza plays the <interference> shot 36 c5!, simultaneously <blocking> the Black b6-queen's defense of the d4-knight and threatening the Black queen herself.

What happens if Gelfand tries 36 ... dxc5 to keep his d4-knight defended? By taking the White c5-pawn, he has opened the c-file for the White c3-rook. Now since Black's c5-pawn is pinned to the c-file, <blocking> the threat of 37 x+, it cannot also <defend> the d4-knight, which vanishes due to 37 x!, exploiting this newly created pin on the c-file.

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Black's 35 ... f5-d4?? made a <LOOSE> piece and 36 c4-c5! closed the line of the defending Black b6-queen (<INTERFERENCE>).

Now in this position, the White c3-rook does -not-, repeat does -not- threaten the <UNDEFENDED> Black c8-rook because the White c3-rook has no <BALEFUL INFLUENCE> -through- the White c5-pawn. That is, the line of attack of the White c3-rook reaches only the c5-square because it is <BLOCKED> by its own White c5-pawn.

But if Black captures the White c5-pawn with 36 ... d6xc5 in order to <DEFEND> his Black d4-knight, then everything changes with regard to the line of attack of the White c3-rook.

(VAR) Position after 36 ... d6xc5:

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Whereas the White c3-rook had no <BALEFUL INFLUENCE> against the <UNDEFENDED> Black c8-rook with a -White- pawn on c5, the White c3-rook now does in fact threaten the <UNDEFENDED> Black c8-rook now that there is a -Black- pawn on c5. <<<That is, that the White c3-rook threatens c8 through the Black c5-pawn but not through the White c5-pawn!>>>

The result of this <BALEFUL INFLUENCE> with the Black pawn being on c5 is that this pawn is <PINNED> against the <UNDEFENDED> Black c8-rook and thus cannot also <DEFEND> the Black d4-knight. Hence 37 a4xd4! wins a whole piece for White.

(VAR) Position after 36 ... d6xc5 37 a4xd4!:

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