This knight check, forking the rook and a-pawn, looks tempting, but the temptation should be resisted. The knight was stronger on d5. The Surgeon added the following comment: As an alternative to 24...Nb4 Black could have tried something like ... Ka7 followed by ...c5 to continue the attack on the White king position. Or another option could have been ...g5 offering an exchange of pawns with the bishop coming to a nice diagonal aimed towards the (White) king. If the exchange is refused then g4 solidifies the h3 pawn.

Exchanging off the knight is good for White here. The White bishop was little more than a handmaiden to the d-pawn. In the resulting position, the White knight will prove superior to the Black bishop because of its ability to change colors. For example, the White knight will be able to threaten the h3 pawn, but the Black bishop will not be able to defend it; hence a rook would have to be expended to defend it. This would put White effectively the exchange up.

Covering the square c4 against rook checks.

Black attacks the isolated d-pawn relentlessly and it would seem that White's opening initiative has evaporated.

Overprotecting the center -- consult Nimzovich's "My System" for more detail.

The tension in the centre threatens to reach critical mass; if White attempts to defend with 29. Kc3, then ... c5 shatters his hope of holding onto the center; Black would force exchanges on d4 and the White king would then be exposed to rook checks on the open c-file, plus a dangerous cross-fire from the bishop on the long diagonal. Not a pretty prospect. White instead makes a counter-demonstration on the other wing, threatening to drive the Black bishop off the long diagonal and back into a submissive position on e7. Oh, and incidentally, the h3 pawn is hanging now.

Black cannot permit g4-g5, so he occupies g5 himself. This however has a downside: it weakens the Black king-side pawns and leaves the bishop on f6 unprotected.

Suddenly White turns Black's flank. "A rook on the seventh is worth a pawn," says an old adage. The immediate threat is Rxf7+ picking up the undefended bishop on f6.

It was this or ... f4-f3, which looked awkward for Black. A possible continuation might have been: 31. ... f4-f3; 32. Rxf7+, Kb6; 33. RxBf6, f3xNe2; 34. Re1, Rxd4; 35. R1xe2, Rxg4; 36. R2xe6, leaving White with an outside passer on the h-file and Black with a c-pawn to defend.

A miscalculation. Black was probably expecting a trade of rooks on the d-file here; it will come, but on White's terms. I rather expected either 33. ... c5 or ... e5; to which I was planning 34. Rf1 to pound away at Black's weakened f7 pawn.