Position after 40 ... ♗d3x♗f1:

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This move is the culmination of an absolutely -fiendish- tactical plan by Nakamura.

It took me quite a while to figure out why Kasimdzhanov (White) played 41 ♔g1-f2 here instead of the obvious 41 ♘e3x♗f1.

Why did White not regain his piece with the obvious recapture 41 ♘e3x♗f1? Because then Black simply plays 41 ... e4-e3!

(VARIATION) Position after 41 ♘e3x♗f1 e4-e3!

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Notice that White cannot stop(!!) the obvious 42 ... e3-e2, <REINFORCING> the <PIN> on the White f1-knight and threatening to <PROMOTE> as well, because the Black e3- and f7-pawns take the d2- and e6-squares, respectively, away from the White d6-rook and the Black e3-pawn takes away the f2-square from the White g1-king!!!!

What an -ingenius- tactical idea by Nakamura! Kasimdzhanov is very sharp tactically and he -completely- missed this idea!

Now notice the sting in the tail! If White moves his g1-king away from the <PINNED> and <LOOSE> White f1-knight with say 42 ♔g1-h2, then Nakamura does not win a piece by grabbing the White f1-knight with 42 ♖c1x♘f1?! but instead plays the stronger 42 ... e3-e2! and the Black e-pawn <PROMOTES>! This is the old <PASSED PAWN VERSUS KNIGHT TRICK>.

(VARIATION) Position after 42 ♔h1-h2 e3-e2!:

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And if White passes with say 42 b4-b5, then once again Nakamura plays 42 ... e3-e2 and the Black e-pawn <PROMOTES>. The Black e-pawn <PROMOTES> no matter what White does!!

So this stupendous variation contains both the <PASSED PAWN VERSUS ROOK TRICK> and the <PASSED PAWN VERSUS KNIGHT TRICK>!